Update specs to be rubocop compliant

- Add rubocop.yml in spec/
- Add spec rubocop test to Strainerfile
- Update specs to comply with rubocop

Change-Id: If38186e6ea9104ef658184812e328368f8b86cea
Addresses: blueprint rubocop-for-dashboard
Merge "Update specs to be rubocop compliant"
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: I376297b7b8995d5c706e27a4388d2352343861db
Partial-Bug: #1195915