Increase udp buffer sizes when installing afs client

Linux default udp buffer sizes are somewhat small if sending much udp
traffic. Openafs uses udp for all of its traffic so we increase the
buffer size to 25MB.

Change-Id: Ie6cb7467c186d5471c71ca876ea9e29a90423bed

roles/openafs-client/files/99-afs-udp.conf

@@ -0,0 +1,2 @@
+net.core.rmem_max=26214400
+net.core.rmem_default=26214400

roles/openafs-client/tasks/main.yaml

@@ -9,6 +9,15 @@
       paths:
         - vars
 
+- name: Increase udp buffer sizes
+  copy:
+    src: 99-afs-udp.conf
+    dest: /etc/sysctl.d/99-afs-udp.conf
+    owner: root
+    group: root
+    mode: '0644'
+  become: yes
+
 - name: Check config path defined
   fail:
     msg: "openafs_client_config_path not defined"