Generate password for wsrep user

* Generate password for wsrep user which is used for galera replication.

Partial-Bug: 1373630
Change-Id: I8025f7272d428d120044c899034d9fbecf8215cc
Signed-off-by: Sergii Golovatiuk <sgolovatiuk@mirantis.com>
Merge "Generate password for wsrep user"