openafs-client: ensure latest package and reorder install

We've noticed that openafs was not getting upgraded to the PPA version
on one of our opendev.org mirrors.  Switch install of packages to
"latest" to make sure it upgrades (reboots to actually apply change
unresolved issue, but at least package is there).

Also, while looking at this, reorder this to install the PPA first,
then ensure we have the kernel headers, then build the openafs kernel
modules, then install.  Add a note about having to install/build the
modules first.

Change-Id: I058f5aa52359276a4013c44acfeb980efe4375a1

roles/openafs-client/tasks/openafs-client/Debian.yaml

@@ -1,11 +1,3 @@
-- name: Install kernel modules
-  package:
-    name:
-      - linux-headers-{{ ansible_kernel }}
-      - openafs-modules-dkms
-    state: present
-  become: yes
-
 # Bionic version is dangerously out of date; use later version.
 #  https://bugs.launchpad.net/ubuntu/+source/openafs/+bug/1832690
 - name: Install openstackci openafs PPA
@@ -14,10 +6,26 @@
   when: ansible_distribution_version is version('18.04', '>=')
   become: yes
 
+- name: Install kernel headers dependency
+  package:
+    name:
+      - linux-headers-{{ ansible_kernel }}
+    state: present
+  become: yes
+
+# NOTE(ianw) : Need to do this first and separately so that the
+# modules are ready for the openafs-client package to start.
+- name: Install openafs kernel modules
+  package:
+    name:
+      - openafs-modules-dkms
+    state: latest
+  become: yes
+
 - name: Install client packages
   package:
     name:
       - openafs-client
       - openafs-krb5
-    state: present
+    state: latest
   become: yes