[Backport 7.61.x] Only set INSTALLATION environment variables when doing injection

[agent-platform-auto-pr]

Backport c5069b5 from #31503.

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What does this PR do?

https://datadoghq.atlassian.net/browse/APMS-14061

We no longer set the environment variables when there is no library to inject (disabled namespace or otherwise).

Motivation

https://docs.google.com/document/d/1PHDp652AmVmNG--cJf0JpV_5OB6evtHZ_qxoZI2z0Pk/edit?tab=t.0

Describe how to test/QA your changes

Tests updated.

[agent-platform-auto-pr]

[Fast Unit Tests Report]

On pipeline 50606621 (CI Visibility). The following jobs did not run any unit tests:

Jobs:

• tests_flavor_dogstatsd_deb-x64
• tests_flavor_heroku_deb-x64
• tests_flavor_iot_deb-x64

If you modified Go files and expected unit tests to run in these jobs, please double check the job logs. If you think tests should have been executed reach out to #agent-devx-help

[agent-platform-auto-pr]

Test changes on VM

Use this command from test-infra-definitions to manually test this PR changes on a VM:

inv create-vm --pipeline-id=50606621 --os-family=ubuntu

Note: This applies to commit dd03f8d

[cit-pr-commenter]

Regression Detector

Regression Detector Results

Metrics dashboard
Target profiles
Run ID: 2cb6157e-5142-47ca-a7ba-7e8250d79291

Baseline: 9c46226
Comparison: dd03f8d
Diff

Optimization Goals: ❌ Regression(s) detected

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
❌	basic_py_check	% cpu utilization	+6.92	[+2.91, +10.92]	1	Logs

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
❌	basic_py_check	% cpu utilization	+6.92	[+2.91, +10.92]	1	Logs
➖	quality_gate_logs	% cpu utilization	+3.48	[+0.45, +6.52]	1	Logs
➖	quality_gate_idle_all_features	memory utilization	+1.96	[+1.82, +2.10]	1	Logs bounds checks dashboard
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	+1.30	[+0.56, +2.04]	1	Logs
➖	otel_to_otel_logs	ingress throughput	+0.29	[-0.40, +0.98]	1	Logs
➖	file_to_blackhole_0ms_latency	egress throughput	+0.05	[-0.76, +0.87]	1	Logs
➖	uds_dogstatsd_to_api	ingress throughput	+0.01	[-0.10, +0.12]	1	Logs
➖	tcp_dd_logs_filter_exclude	ingress throughput	-0.00	[-0.01, +0.01]	1	Logs
➖	file_to_blackhole_100ms_latency	egress throughput	-0.02	[-0.79, +0.75]	1	Logs
➖	file_to_blackhole_500ms_latency	egress throughput	-0.05	[-0.82, +0.72]	1	Logs
➖	file_to_blackhole_300ms_latency	egress throughput	-0.07	[-0.70, +0.56]	1	Logs
➖	file_to_blackhole_1000ms_latency_linear_load	egress throughput	-0.16	[-0.62, +0.30]	1	Logs
➖	tcp_syslog_to_blackhole	ingress throughput	-0.23	[-0.29, -0.16]	1	Logs
➖	quality_gate_idle	memory utilization	-0.27	[-0.31, -0.22]	1	Logs bounds checks dashboard
➖	file_to_blackhole_1000ms_latency	egress throughput	-0.49	[-1.27, +0.29]	1	Logs
➖	file_tree	memory utilization	-0.61	[-0.76, -0.47]	1	Logs
➖	pycheck_lots_of_tags	% cpu utilization	-1.92	[-5.38, +1.54]	1	Logs

Bounds Checks: ✅ Passed

perf	experiment	bounds_check_name	replicates_passed	links
✅	file_to_blackhole_0ms_latency	lost_bytes	10/10
✅	file_to_blackhole_0ms_latency	memory_usage	10/10
✅	file_to_blackhole_1000ms_latency	memory_usage	10/10
✅	file_to_blackhole_1000ms_latency_linear_load	memory_usage	10/10
✅	file_to_blackhole_100ms_latency	lost_bytes	10/10
✅	file_to_blackhole_100ms_latency	memory_usage	10/10
✅	file_to_blackhole_300ms_latency	lost_bytes	10/10
✅	file_to_blackhole_300ms_latency	memory_usage	10/10
✅	file_to_blackhole_500ms_latency	lost_bytes	10/10
✅	file_to_blackhole_500ms_latency	memory_usage	10/10
✅	quality_gate_idle	memory_usage	10/10	bounds checks dashboard
✅	quality_gate_idle_all_features	memory_usage	10/10	bounds checks dashboard
✅	quality_gate_logs	lost_bytes	10/10
✅	quality_gate_logs	memory_usage	10/10

Explanation

Confidence level: 90.00%
Effect size tolerance: |Δ mean %| ≥ 5.00%

Performance changes are noted in the perf column of each table:

• ✅ = significantly better comparison variant performance
• ❌ = significantly worse comparison variant performance
• ➖ = no significant change in performance

A regression test is an A/B test of target performance in a repeatable rig, where "performance" is measured as "comparison variant minus baseline variant" for an optimization goal (e.g., ingress throughput). Due to intrinsic variability in measuring that goal, we can only estimate its mean value for each experiment; we report uncertainty in that value as a 90.00% confidence interval denoted "Δ mean % CI".

For each experiment, we decide whether a change in performance is a "regression" -- a change worth investigating further -- if all of the following criteria are true:

1. Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.

2. Its 90.00% confidence interval "Δ mean % CI" does not contain zero, indicating that if our statistical model is accurate, there is at least a 90.00% chance there is a difference in performance between baseline and comparison variants.

3. Its configuration does not mark it "erratic".

CI Pass/Fail Decision

✅ Passed. All Quality Gates passed.

• quality_gate_logs, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_logs, bounds check lost_bytes: 10/10 replicas passed. Gate passed.
• quality_gate_idle, bounds check memory_usage: 10/10 replicas passed. Gate passed.
• quality_gate_idle_all_features, bounds check memory_usage: 10/10 replicas passed. Gate passed.