Set Galera user password same as MySQL root

* Use MySQL root password for Galera state transfer user which is
randomly generated rather than static one

Closes-bug: 1373630
Closes-Bug: 1349460

Change-Id: I0612e5ff862526ea385cf43b517e13f4c2f1d702
Signed-off-by: Sergii Golovatiuk <sgolovatiuk@mirantis.com>
Merge "Set Galera user password same as MySQL root"