Workflows should have `concurrency` to prevent multiple runs

[Bradley A. Thornton]

Something like this:

concurrency:
  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
  cancel-in-progress: true

was noticed with ack after several rapid PR changes

[Bradley A. Thornton]

Concurrency does work the way one might expect in a reusable workflow. It will end up cancelling any other use of the work flow.

So the concurrency need to be in the calling repo. e.g. ansible-collections/ansible.scm#151