openafs-client: use dnf for CentOS 8

We are seeing some failures that seem to add up to the yum module not
detecting a failure installing the kernel modules for openafs.  See if
this works better with "dnf", which is the native package installer on
CentOS 8.

Change-Id: I82588ed5a02e5dff601b41b27b28a663611bfe89

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

@@ -28,7 +28,7 @@
     gpgcheck: '{{ openafs_client_yum_repo_gpg_check }}'
   become: yes
 
-- name: Install kernel modules
+- name: Install kernel modules CentOS 7
   yum:
     name:
       - kernel-devel
@@ -38,6 +38,19 @@
     enablerepo: epel  # dkms
     state: present
   become: yes
+  when: ansible_distribution_version is version('8', '<')
+
+- name: Install kernel modules CentOS 8
+  dnf:
+    name:
+      - kernel-devel
+      - dkms
+      - gcc
+      - dkms-openafs
+    enablerepo: epel  # dkms
+    state: present
+  become: yes
+  when: ansible_distribution_version is version('8', '>=')
 
 - name: Install client
   yum: