access: fix VLAN database idempotency

Do not try and match the global VLAN list as printed by the switch.
Instead, only try to realize the truth: there may be some VLANs added
and some removed.

We keep the compact_numlist filter and use it instead of the built-in
vlan_parser when listing VLANs for tagged ports. This is because some
switches compact 1,2,4,5,6 as 1-2,4-6 and others as 1,2,4-6 (see next
commit).

All of this should reduce the number of cases where Ansible reports a
change in configuration where there was in fact no change.

roles/access/tasks/main.yml

@@ -11,6 +11,20 @@
   set_fact:
     snmp_engine_id: '{{ (serial | sha1)[:24] }}'
 
+- name: Get switch facts
+  cisco.ios.ios_facts:
+    gather_subset: config
+
+# Determine VLANs to add and remove from switch.
+- set_fact:
+    actual_vlans: "{{ vlans | map(attribute='vid') }}"
+    switch_vlans: "{{ ansible_net_config | split('\n') | select('match', '^ *vlan (range )?[0-9]')
+        | map('regex_search', '[0-9,-]+') | join(',') | ansible.netcommon.vlan_expander }}"
+
+- set_fact:
+    add_vlans: "{{ actual_vlans | difference(switch_vlans) }}"
+    del_vlans: "{{ switch_vlans | difference(actual_vlans) }}"
+
 - name: Set configuration
   ansible.netcommon.cli_config:
     config: '{{ lookup("template", "config-"~manufacturer~"-"~device_type~".j2") }}'