Added conditional statements for installed packages

Packages required to use this module may also be declared
in downstream manifests. This patch adds necessary if conditions,
to ensure these do not cause conflicts.

Change-Id: I3c1b6cbd5743a8331752bfe4dcb33267ddcf840d

manifests/client.pp

@@ -27,18 +27,34 @@ class openafs::client (
   if ($::osfamily == 'RedHat') {
     $openafs_path = '/usr/vice/etc'
 
-    $dkms_packages = [
-      'kernel-devel',
-      'dkms',
-      'gcc'
-    ]
+    if ! defined(Package['kernel-devel']) {
+      package { 'kernel-devel':
+        ensure => present,
+        before => [
+          Package['openafs-client'],
+          Package['openafs-krb5'],
+        ],
+      }
+    }
 
-    package { $dkms_packages:
-      ensure => present,
-      before => [
-        Package['openafs-client'],
-        Package['openafs-krb5'],
-      ],
+    if ! defined(Package['dkms']) {
+      package { 'dkms':
+        ensure => present,
+        before => [
+          Package['openafs-client'],
+          Package['openafs-krb5'],
+        ],
+      }
+    }
+
+    if ! defined(Package['gcc']) {
+      package { 'gcc':
+        ensure => present,
+        before => [
+          Package['openafs-client'],
+          Package['openafs-krb5'],
+        ],
+      }
     }
 
     package { 'dkms-openafs':