Improve guest agent when start
Improve guest agent when start

If we run guest agent, sometime it can't connect to database because
root user was secure with password make can't right work.

I hope this path will improve it by get password of root user to
authenticate with database

Task: #42105
Story: #2008746
Change-Id: I666120fc9df8d1c0bea72dee95763c2462e256ca

openstack/trove,openstack/trove