Flush handlers at the end of the role

[abelfodil]

This ensures the syncconf is called at the end of the role before moving on, otherwise it's only called at the end of the play.

The code would look like:

- name: Force all notified handlers to run
  meta: flush_handlers

[githubixx]

I'm thinking about it. But it'd be definitely optional as it'd change the current behavior of the role. So adding a variable like wireguard_flush_handlers: true|false might be an option.