support playbooks which use gather_facts: false

Some users prefer to use `gather_facts: false` in their playbooks.
However, the network role requires certain ansible_facts to be set.  If
the user wants to use the network role with `gather_facts: false`, the
role will gather the minimum subset of facts required.  If the user does
not want the role to gather facts, the user can either not use the
network role, or ensure that all required facts are in the facts cache.

Signed-off-by: Rich Megginson <rmeggins@redhat.com>

tasks/main.yml

@@ -1,6 +1,13 @@
 # SPDX-License-Identifier: BSD-3-Clause
 # get service facts, used in defaults/main.yml
 ---
+- name: Ensure ansible_facts used by role
+  setup:
+    gather_subset: min
+  when: not ansible_facts.keys() | list |
+    intersect(__network_required_facts) == __network_required_facts
+  no_log: true
+
 - name: Check which services are running
   service_facts:
   no_log: true