bugfixes:
- mysql_user - Correct procedure to check existing TLS requirements.
- mysql_user - Minor syntax fixes.
improvements:
- mysql_user - Added tests to verify that TLS requirements are removed with an empty `tls_requires` parameter.
- mysql_user - Added examples on how to remove TLS requirements by setting an empty `tls_requires` parameter.
- mysql_user - Refactored TLS requirement tests into their own file.