Always try to use the latest virtualenv

Instead of fixing on an old version of virtualenv that is
fixed at 1.11.4 which has an older version of pip (which does not
like the new version specifications) we should always try to use
the latest to ensure that we find bugs early, and also so that we
can parse the new version specifications without dying.

Change-Id: I73c981a9683868455c3326c4e9aebe50608ae184

modules/openstack_project/manifests/base.pp

@@ -60,15 +60,9 @@ class openstack_project::base(
   }
 
   include pip
-  $desired_virtualenv = '1.11.4'
 
-  if (( versioncmp($::virtualenv_version, $desired_virtualenv) < 0 )) {
-    $virtualenv_ensure = $desired_virtualenv
-  } else {
-    $virtualenv_ensure = present
-  }
   package { 'virtualenv':
-    ensure   => $virtualenv_ensure,
+    ensure   => latest,
     provider => pip,
     require  => Class['pip'],
   }