Interaction between multiple Actors causes Test Case to hang

[tachyonics]

Describe the bug
Some interaction between two different actors will cause a unit test that uses both to hang and not complete.

To Reproduce
Steps to reproduce the behavior:

1. Checkout https://github.com/amzn/smoke-framework-examples/tree/aws_sdk_swift
2. Compile and run the tests for PersistenceExampleService
3. A number of the tests - such as AddCustomerEmailAddressTests.testAddCustomerEmailAddress will hang and not complete
   ...

Expected behavior
The test case should complete and succeed as with the main branch of https://github.com/amzn/smoke-dynamodb

Screenshots
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Environment (please complete the following information):

• OS: [e.g. macOS 11.0] Ubuntu, Swift 5.6.1
• Xcode Version/Tag/Branch:

https://github.com/amzn/smoke-framework-examples/runs/6959594337?check_suite_focus=true

Additional context
Add any other context about the problem here.