Move apt cache update to individual task per role

Move apt cache update to individual task per role

The apt-cache update can fail due to transient issues related to the
action being a network operation. To reduce the impact of these
transient failures this patch adds a retry to the update_cache task.

However, the apt_repository tasks which would perform an apt_update
won't retry the apt_update on a failure in the same way, as such this PR
moves the apt_update into an individual task, once per role.

Finally, the apt_repository tasks no longer have a changed_when: false,
and the apt_cache update is only performed once per role, if the
repositories change. Otherwise the cache is updated on the "apt" install
tasks if the cache_timeout has been reached.