Modifies Keystone to use same MySQL DB as RO

ro-db is renamed to mysql

There is no benefit of having multiple sql database engines. All components
should share the same. This is part of the effort to make OSM components
support an HA scenario. Unifying sql db engines, allows to have them all
connected to a database cluster, for example.

Change-Id: I5d0f2b75da9ea7c6bbb341cac3cb899b4821dd40
Signed-off-by: Benjamin Diaz <bdiaz@whitestack.com>