nxos_vlan: fix broken purge behavior (issue #57101) (#57229)

* nxos_vlan: fix broken purge behavior (issue #57101)

Symptoms/Analysis:
- `nxos_vlan` `purge: true` would fail when `purge` was trying to delete all unspecified vlans, including vlan 1.
- `nxos` devices do not allow removing vlan 1 and raise a cli exception error
- Previous fix #55144 caused a side effect when `purge` was used: vlan changes specified by `aggregate` were ignored; e.g.
 - vlan 4 is not present; playbook specifies `aggregate: { vlan: 4 }, purge: true`
 - results in proper purging but vlan 4 is not created

Solutions:
- ignore vlan 1 when purging
- remove the `not purge` check from state present logic

Added additional unit tests and integration tests.
Tested against all regression platforms.

* PEP fixes

* Add agg_show_vlan_brief.txt fixture

* Add warning for removing vlan 1

* change method name check

test/integration/targets/nxos_vlan/tests/common/agg.yaml

@@ -8,6 +8,7 @@
     lines:
       - no vlan 102
       - no vlan 103
+      - no vlan 104
     provider: "{{ connection }}"
   ignore_errors: yes
 
@@ -84,8 +85,38 @@
     that:
       - 'result.changed == false'
 
+- name: "setup for purge test with aggregate add"
+  nxos_vlan:
+    vlan_id: 104
+    purge: true
+    provider: "{{ connection }}"
+
+- name: purge 104 with aggregate add 102-103
+  nxos_vlan: &purge_add
+    aggregate:
+      - { vlan_id: 102 }
+      - { vlan_id: 103 }
+    purge: true
+    provider: "{{ connection }}"
+  register: result
+
+- assert:
+    that:
+      - 'result.changed == true'
+      - '"vlan 102" in result.commands'
+      - '"vlan 103" in result.commands'
+      - '"no vlan 104" in result.commands'
+
+- name: purge_add - Idempotence
+  nxos_vlan: *purge_add
+  register: result
+
+- assert:
+    that:
+      - 'result.changed == false'
+
 - name: teardown
   nxos_config: *rm
   ignore_errors: yes
 
-- debug: msg="END connection={{ ansible_connection }}/agg.yaml" 
+- debug: msg="END connection={{ ansible_connection }}/agg.yaml"

test/integration/targets/nxos_vlan/tests/common/sanity.yaml

@@ -134,7 +134,6 @@
   - assert: *false
     when: platform is search('N3K|N7K')
 
-# Uncomment this once the get_capabilities() work on nxapi as well
   - name: Change mode
     nxos_vlan: &mode1
       vlan_id: 50