Ensure pip updates to latest release

I mistakenly assumed in I2b5822a7383b8f2f49958c8268453333dabe52cc that
this module would update the installed version of bandersnatch.
Installing from pip, we want to get the latest release.

Change-Id: I6a1f213a3127f57b41b4ec7e3f128b1bbde2ae37

manifests/init.pp

@@ -28,7 +28,7 @@ class bandersnatch (
 
   if ($bandersnatch_source == 'pip') {
     package { 'bandersnatch':
-      ensure   => 'present',
+      ensure   => latest,
       provider => openstack_pip,
     }
   } else {