common: set apt pinning with Red Hat Ceph Storage

When `ceph_stable_rh_storage` is True, every cluster node should have a
`/etc/apt/preferences.d/rhcs.pref` file with the following contents:

```
Explanation: Prefer Red Hat packages
Package: *
Pin: release o=/Red Hat/
Pin-Priority: 999
```

ceph-deploy already did this when used with ice-setup, and we need to do
the same thing with the ceph-ansible stack.

Closes: #1182 and https://bugzilla.redhat.com/show_bug.cgi?id=1404515

Signed-off-by: Sébastien Han <seb@redhat.com>

roles/ceph-common/tasks/installs/install_rh_storage_on_debian.yml

@@ -25,6 +25,14 @@
     - ceph_rhcs
     - ceph_rhcs_iso_install
 
+- name: set apt pinning for red hat ceph storage
+  template:
+    src: "{{ role_path }}/templates/rhcs.pref.j2"
+    dest: /etc/apt/preferences.d/rhcs.pref
+    owner: root
+    group: root
+    mode: 0644
+
 - name: add the red hat storage apt-key
   apt_key:
     data: "{{ lookup('file', role_path+'/files/cephstablerhcs.asc') }}"

roles/ceph-common/templates/rhcs.pref.j2

@@ -0,0 +1,7 @@
+#jinja2: trim_blocks: "true", lstrip_blocks: "true"
+# {{ ansible_managed }}
+
+Explanation: Prefer Red Hat packages
+Package: *
+Pin: release o=/Red Hat/
+Pin-Priority: 999