Allow nodepool standalone puppet install

Installing nodepool standalone has this error:
 Could not find dependency Class[Pip] for Exec[install_nodepool] at
 /root/config/modules/nodepool/manifests/init.pp:90

Add the missing include pip statement.

Change-Id: Id30814eb1788e7b7eb533794a26c231000e9b41c

modules/nodepool/manifests/init.pp

@@ -81,6 +81,7 @@ class nodepool (
     source   => $git_source_repo,
   }
 
+  include pip
   exec { 'install_nodepool' :
     command     => 'pip install /opt/nodepool',
     path        => '/usr/local/bin:/usr/bin:/bin/',