tests: Fix tests_network_state_nm.yml CI failure

Since the merge of nmstate commit 'nm dns: Support appending static DNS
before dynamic DNS' (https://github.com/nmstate/nmstate/pull/2438),
nmstate treats interface with `auto-dns: true` as valid to store DNS
and tries to use NetworkManager global DNS as much as possible. However,
in NM, `dns=systemd-resolved` does not support global DNS configuration,
because systemd-resolved only supports per-interface DNS servers (via
the D-Bus API). Therefore, write and validate the DNS configuration in
/run/NetworkManager/no-stub-resolv.conf, which contains the original
DNS settings pushed to the DNS plugin.

Signed-off-by: Wen Liang <liangwen12year@gmail.com>

tests/playbooks/tests_network_state.yml

@@ -130,31 +130,6 @@
           - route.stdout is search("table-id:(\s+)254")
         msg: the route configuration does not contain the specified route
 
-    - name: Set the DNS processing mode and the resolv.conf management mode
-      lineinfile:
-        path: /etc/NetworkManager/NetworkManager.conf
-        line: "rc-manager=unmanaged\ndns=systemd-resolved"
-        insertafter: \[main\]
-
-    - name: Restart the NetworkManager
-      service:
-        name: NetworkManager
-        state: restarted
-
-    - name: Install the systemd-resolved
-      package:
-        name: systemd-resolved
-        state: present
-        use: "{{ (__network_is_ostree | d(false)) |
-          ternary('ansible.posix.rhel_rpm_ostree', omit) }}"
-      when:
-        - ansible_distribution_major_version | int > 8
-
-    - name: Enable the systemd-resolved service
-      service:
-        name: systemd-resolved
-        enabled: true
-
     - name: Configure the DNS
       import_role:
         name: linux-system-roles.network
@@ -174,16 +149,10 @@
       ignore_errors: true  # noqa ignore-errors
       changed_when: false
 
-    - name: Get the DNS configuration from the file `/etc/resolv.conf`
-      command: cat /etc/resolv.conf
-      register: resolvconf
-      ignore_errors: true  # noqa ignore-errors
-      changed_when: false
-
-    - name: Check if `/etc/resolv.conf` is generated by NM
-      command: grep "Generated by NetworkManager" /etc/resolv.conf
-      register: generate_by_nm
-      ignore_errors: true  # noqa ignore-errors
+    - name: Get the DNS configuration from the file
+        `/run/NetworkManager/no-stub-resolv.conf`
+      command: cat /run/NetworkManager/no-stub-resolv.conf
+      register: no_stub_resolvconf
       changed_when: false
 
     - name: Assert that the nmstatectl contains the specified DNS configuration
@@ -194,24 +163,15 @@
           - nmstatectl.stdout is search("2001:4860:4860::8888")
         msg: the nmstatectl does not contain the specified DNS configuration
 
-    - name: Assert that the file `/etc/resolv.conf` does not contain the
-        specified DNS configuration
+    - name: Assert that the file `/run/NetworkManager/no-stub-resolv.conf`
+        contains the specified DNS configuration
       assert:
         that:
-          - resolvconf.stdout is not search("example.com") and
-            resolvconf.stdout is not search("example.org") and
-            resolvconf.stdout is not search("2001:4860:4860::8888") or
-            generate_by_nm.stdout | length == 0
-        msg: the file `/etc/resolv.conf` contains the specified DNS
-          configuration
-
-    - name: "** TEST check resolvectl"
-      command: resolvectl
-      register: result
-      until: "'example.com' in result.stdout"
-      retries: 20
-      delay: 2
-      changed_when: false
+          - no_stub_resolvconf.stdout is search("example.com")
+          - no_stub_resolvconf.stdout is search("example.org")
+          - no_stub_resolvconf.stdout is search("2001:4860:4860::8888")
+        msg: the file `/run/NetworkManager/no-stub-resolv.conf` does not
+          contain the specified DNS configuration
 
     - name: Include the task 'delete_interface.yml'
       include_tasks: tasks/delete_interface.yml