Pass zuul_revision through to zuul_scheduler class

We would currently pass it to the zuul_merger but not the scheduler,
this would end up making the zuul version installed to fall back to
master instead of whatever is specified.

Change-Id: If2ca48ce15238583b63024cdf5c1bd754d60203c

manifests/single_node_ci.pp

@@ -221,6 +221,7 @@ class openstackci::single_node_ci (
     smtp_host            => $smtp_host,
     smtp_default_from    => $smtp_default_from,
     smtp_default_to      => $smtp_default_to,
+    revision             => $zuul_revision,
   }
 
   class { '::openstackci::nodepool':