Build Farm - Tolerance flakiness in TestMultiThreadedExecutor

[piraka9011]

Bug report

Required Info:

• Operating System: OS X
• Installation type: Source (Build Farm)
• Version or commit hash: bf89dc0
• DDS implementation: FastRTPS
• Client library (if applicable): rclcpp

Steps to reproduce issue

Run the build farm. TestMultiThreadExecutor fails due to tolerance.

Expected behavior

TestMultiThreadExecutor passes.

Actual behavior

TestMultiThreadExecutor fails.

A recent build in the Nightly OS X - Release failed because the tolerance in the TestMultiThreadExecutor was too low.
Should the tolerance be increased the test is running on an OS X system or is there another way to minimize flakiness?

[jacobperron]

Based on the comment here, we may consider relaxing the test to check that more than X seconds has passed and not have an upper bound:

-  if (diff < PERIOD - TOLERANCE || diff > PERIOD + TOLERANCE) {
+  if (diff < PERIOD - TOLERANCE) {