ducktape/test_simple_live_change: wait for all nodes

[BenPope]

The test is checking config status, but it is not waiting for the status object to have content for all the expected nodes.

Fixes #10977

Backports Required

• none - not a bug fix
• none - this is a backport
• none - issue does not exist in previous branches
• none - papercut/not impactful enough to backport
• v23.1.x
• v22.3.x
• v22.2.x

Not seen on v23.1.x in the last 14d / 55 runs.

Release Notes

• none

[BenPope]

Tested locally.

Without:

SESSION REPORT (ALL TESTS)
ducktape version: 0.8.8
session_id:       2023-06-01--046
run time:         2 minutes 59.723 seconds
tests run:        100
passed:           87
failed:           13
ignored:          0
opassed:          0
ofailed:          0

With this fix:

ducktape version: 0.8.8
session_id:       2023-06-01--047
run time:         30 minutes 27.879 seconds
tests run:        1000
passed:           1000
failed:           0
ignored:          0
opassed:          0
ofailed:          0

[dotnwat]

lgtm

[BenPope]

CI failures:

• CI Failure (failed to hydrate chunk starting at 0) in CloudStorageTimingStressTest.test_cloud_storage_with_partition_moves #10868
• CI Failure (retries) in rptest.tests.e2e_iam_role_test #11107 (x3)
• CI Failure (AddressSanitizer crash) in ShortLivedCredentialsTest.test_short_lived_credentials #11095
• CI Failure (TimeoutError) in CloudStorageChunkReadTest.test_read_when_segment_size_smaller_than_chunk_size #11151
  New CI failures:
• CI Failure (error querying metrics) in RandomNodeOperationsTest.test_node_operations #11158 (unrelated)