Thread.sleep used in some unit tests; consider replacing with Awaitility

[dlg99]

Thread.sleep used in some unit tests (search code for it); consider replacing with Awaitility.

This is a follow up on #22 (comment)

Priority is fairly low IMO - occurences of this are very limited, test run reasonably fast AFAICT, it's unclear what specifically the tests have to wait for etc.

[mattisonchao]

I will fix it @dlg99