Add the creation of /var/run/openstack when zeromq is chosen

Fixed Bug 1200539.

Change-Id: I270623da7026e94d9ece4d5f510cad5a6c4d79ff
diff --git a/lib/rpc_backend b/lib/rpc_backend
index ff87aae..63edc07 100644
--- a/lib/rpc_backend
+++ b/lib/rpc_backend
@@ -131,6 +131,9 @@
         else
             exit_distro_not_supported "zeromq installation"
         fi
+        # Necessary directory for socket location.
+        sudo mkdir -p /var/run/openstack
+        sudo chown $STACK_USER /var/run/openstack
     fi
 }