openstack-db: support updating mysql password in newer conf files

In some cases the distribution config may be in
/usr/share/nova/nova-dist.conf for example, with
a corresponding setting in /etc/nova/nova.conf.
By default this corresponding setting is commented out.
openstack-db: Output info about the possibly lengthy sync operation

Initializing the database can take a significant amount of time,
therefore output a  informational message to wait...
openstack-db: prompt users on how to clear a partially installed db

It's quite awkward to remove all remnants of each service's database,
so add a check for users and if found, prompt with how to reinitialize
the database.  We could auto --drop in this case, but that's too risky,
so the decision is left to the operator.
openstack-status: look for mysql in the correct config files