linux-embedded time unit tests are flaky

[andy31415]

Problem

https://app.circleci.com/pipelines/github/project-chip/connectedhomeip/529/workflows/844b2bc4-3426-4d72-85ea-e6296cdc686c/jobs/4659

failed but succeeded on re-run. Logs say:

======================================================
   Chip g351fa47: src/platform/tests/test-suite.log
======================================================
 
# TOTAL: 2
# PASS:  1
# SKIP:  0
# XFAIL: 0
# FAIL:  1
# XPASS: 0
# ERROR: 0
 
.. contents:: :depth: 2
 
FAIL: TestPlatformTime
======================
 
[ CHIP DeviceLayer tests ]
Failed assert: Tdelta < (Tdelay + margin) in ../../../../../src/platform/tests/TestPlatformTime.cpp:116
Failed assert: Tdelta < (Tdelay + margin) in ../../../../../src/platform/tests/TestPlatformTime.cpp:116
[ CHIP DeviceLayer tests : Test DeviceLayer::GetClock_Monotonic      ] : FAILED
[ CHIP DeviceLayer tests : Test DeviceLayer::GetClock_MonotonicMS    ] : PASSED
[ CHIP DeviceLayer tests : Test DeviceLayer::GetClock_MonotonicHiRes ] : PASSED
Failed Tests:   1 / 3
Failed Asserts: 2 / 21
FAIL TestPlatformTime (exit status: 255

Proposed Solution

Need to investigate flakyness cause and fix it. I did not check, but guessing that if this forwards to a real clock, then execution speed may matter and on things like qemu things may not be as fast.

[woody-apple]

Closing as duplicate of this.
#861

@turon ?