purge-docker: added conditionals needed to successfully re-run purge

purge-docker: added conditionals needed to successfully re-run purge

Added 'ignore_errors: true' to multiple lines which run docker commands; even in cases where docker is no longer installed. Because of this, certain tasks in the purge-docker-cluster.yml will cause the playbook to fail if re-run and stop the purge. This leaves behind a dirty environment, and a playbook which can no longer be run.
Fix Regex line 275: Sometimes 'list-units' will output 4 spaces between loaded+active. The update will account for both scenarios.
purge fetch_directory: in other roles fetch_directory is hard linked ex.: "{{ fetch_directory }}"/"{{ somedir }}". That being said, fetch_directory will never have a trailing slash in the all.yml so this task was never being run(causing failures when trying to re-deploy).

Signed-off-by: Randy J. Martinez <ramartin@redhat.com>
(cherry picked from commit d1f2d64b15479524d9e347303c8d5e4bfe7c15d8)
Signed-off-by: Sébastien Han <seb@redhat.com>