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: I8e1e25e73eb01cbea30435fe7c6c53cab7a15c04
Partial-Bug: #1195915