Fix incomplete timestamp support and wait_for_valid_timestamp not ret…

[WayneDroid]

• [x] This contribution adheres to CONTRIBUTING.md.

What does this Pull Request accomplish?

• removed timestamp attributes from exclusion list.
• return timestamp value from wait_for_valid_timestamp().
• updated unit test cases

Why should this Pull Request be merged?

Closes #591

What testing has been done?

run poetry run pytest tests/ -q - pass

[zhindes]

FYI - I updated your PR description to use the closes keyword for the issue!