Something that happens fairly frequently for folks is a network failure when Trellis tries to add the PPA for PHP, MariaDB, or Nginx. The failure looks like this:

TASK [php : Add PHP PPA] *******************************************************
fatal: [default]: FAILED! => {"changed": false, "msg": "failed to fetch PPA information, error was: Connection failure: The read operation timed out"}

The provisioning will sometimes continue a bit further before ending in a failure, and you're left with an unusable VM. Almost always, immediately trying to re-provision will work without an issue.

This PR adds 3 retries to any failures when trying to add a PPA.