Improve readability of swift::xfs

Improve readability of swift::xfs using ensure_packages
from the stdlib.

Change-Id: I9550c6e9415e49b5363e21c73c935390c3a635e3

manifests/xfs.pp

@@ -2,14 +2,8 @@
 # package dependencies for creating
 # xfs partitions
 class swift::xfs {
-  if !defined(Package['xfsprogs']){
-    package { 'xfsprogs':
-      ensure => present
-    }
-  }
-  if !defined(Package['parted']){
-    package { 'parted':
-      ensure => present
-    }
-  }
+
+  $packages = ['xfsprogs', 'parted']
+  ensure_packages($packages)
+
 }