Wait until MySQL is ready before running OSTF

Check that MySQL Galera is ready on primary
controller before performing OSTF checks to avoid
MySQL connection error from keystoneclient.
Also, one OSTF test will fail because one compute
node is down, so need to add it to should_fail.

Change-Id: Id42abbf822f9bc51402f64ddedd1a6903260f977
Closes-bug: #1337298
Merge "Wait until MySQL is ready before running OSTF"