Optimize github tests

[ohdearaugustin]

Only run the molecule test if there was a change in the role.
Currently all molecule tests will run on a push or pullrequest, even thou nothing was changed in the role.

Something like that would be nice:

on:
  push:
    paths:
    - 'folder1/**'
  pull_request:
    paths: 
    - 'folder1/**'

This will shorten the run time of the tests and lower cost of test.

Maybe also add approval for pull request. So the test are not executed automatically.

[MarkusTeufelberger]

This is partially by design, as some roles depend on external state (e.g. newer/updated packages in repos). splitting tests by role is possible, but since tests are currently run in parallel anyways, the only speedup would be from testing faster than the current slowest role test.

Tests only run automatically for users from the mgit organization.