Newer mysql cli clients emit a warning when you put a password on the
cli. This warning was being interpreted as a failure by the test
framework. Change the framework to accept the warning or empty string as
valid responses when running the mysql cli client to support using the
cli client in the trove tests.
I am not entirely sure when this new behavior arrived in mysql but it is
present in Ubuntu Xenial's Mysql 5.7 packages.
Change-Id: Ia148d72a7646f4c424139232d6388ff14d1d8686
Clark Boylan
c4f29c0e17