Rubocop cleanup - use single .rubocop.yml file

- Remove individual directory/.rubocop.yml file
- Adjust .rubocop.yml to include all other directories
- Adjust Strainerfile to use the single .rubocop.yml file

Change-Id: Id64fae024f8972e87919f837f31f487a43744d5f
Addresses: blueprint rubocop-for-dashboard