Backport of Fix TestDNS_ServiceLookup_ARecordLimits so that it only creates test agents the minimal amount of time into release/1.19.x

[dhiaayachi]

Backport

This PR is auto-generated from hashicorp#21608 to be assessed for backporting due to the inclusion of the label backport/1.19.

The below text is copied from the body of the original PR.

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Description

TestDNS_ServiceLookup_ARecordLimits is one of our longest running tests.

It's average runtime in CI over the last 3 months is 1min 45 secs.

Locally on a mac M1, it performs in 1 min 11 seconds:

The reason why is that for every test case it spawns a new TestAgent. This is 112 test agents getting spawned, taking up ports, file descriptors, etc.

Re-arranging this test so that test agents are only created when the agent config changes, reduces it to 7 Test Agents getting created. (There was also a category of tests that could be removed as duplicates that removed 28 of the test agent).

This is the test results locally now that finish in 10 secs:

Testing & Reproduction steps

Links

PR Checklist

• updated test coverage
• external facing docs updated
• appropriate backport labels added
• not a security concern

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Overview of commits

• 0ca8552 - ff2713b - f8c8d0a - da2c449 - 38e824a - 8cf76bd