Move to use "get_password" instead of "{user,service,db}_password"

The user_password, service_password and db_password functions are redundant
since they simply call "secret". Creates a get_password function that will
accept a "type" of db, service or user.

All instances of these calls have been changed to call get_password

Change-Id: Ic73c99034638ec092192d11e37671edbba0e48ef
Partial-Bug: #1195915
Merge "Move to use "get_password" instead of "{user,service,db}_password""