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: I6879cac6731cc167592820caa811c2cc30660af0
Partial-Bug: #1195915