Add code to unmount /etc/resolv.conf in Molecule prepare stage

Docker bind mounts a file from the host to /etc/resolv.conf.  This is
inconvenient for us, since we need to create a symlink at
/etc/resolv.conf.  At the same time, we don't want to break DNS.  The
playbook being imported contains a workaround for this situation.

molecule/default/prepare.yml

@@ -1,3 +1,11 @@
 ---
 - name: Import upgrade playbook
   ansible.builtin.import_playbook: upgrade.yml
+
+# Docker bind mounts a file from the host to /etc/resolv.conf.  This
+# is inconvenient for us, since we need to create a symlink at
+# /etc/resolv.conf.  At the same time, we don't want to break DNS.
+# The playbook being imported contains a workaround for this
+# situation.
+- name: Unmount /etc/resolv.conf
+  ansible.builtin.import_playbook: unmount.yml

molecule/default/unmount.yml

@@ -0,0 +1,26 @@
+---
+- name: Unmount /etc/resolv.conf
+  hosts: all
+  become: true
+  become_method: ansible.builtin.sudo
+  tasks:
+    - name: Copy /etc/resolv.conf to /tmp
+      ansible.builtin.copy:
+        dest: /tmp/resolv.conf
+        group: root
+        mode: u=rw,g=r,o=r
+        owner: root
+        remote_src: true
+        src: /etc/resolv.conf
+    - name: Unmount /etc/resolv.conf
+      ansible.posix.mount:
+        path: /etc/resolv.conf
+        state: unmounted
+    - name: Copy /tmp/resolv.conf to /etc
+      ansible.builtin.copy:
+        dest: /etc/resolv.conf
+        group: root
+        mode: u=rw,g=r,o=r
+        owner: root
+        remote_src: true
+        src: /tmp/resolv.conf