Ensure that apt is always chosen on debian/ubuntu (#44413)

One can install alternate packages managers on debuntu machines.
However, doing so doesn't mean you want to suddenly start using them.

Add in a check similar to the fedora yum/dnf check that sets apt as the
pkg_mgr if the ansible_os_family is Debian.

test/integration/targets/package/tasks/main.yml

@@ -46,6 +46,30 @@
       setup:
   when: ansible_distribution == "Fedora"
 
+# Verify correct default package manager for Debian/Ubuntu when Zypper installed
+- block:
+    # Just make an executable file called "zypper" - installing zypper itself
+    # consistently is hard - and we're not going to use it
+    - name: install fake zypper
+      file:
+        state: touch
+        mode: 0755
+        path: /usr/bin/zypper
+    - name: gather facts again
+      setup:
+    - name: validate output
+      assert:
+        that:
+          - 'ansible_pkg_mgr == "apt"'
+  always:
+    - name: remove fake zypper
+      file:
+        path: /usr/bin/zypper
+        state: absent
+    - name: gather facts again
+      setup:
+  when: ansible_os_family == "Debian"
+
 ##
 ## package
 ##