fix for Bug 1029015.Added single quotes to remove unnecessary space in msg

Change-Id: Iabf521f59140aa5afc1649d66760b9323dc03687
diff --git a/tempest/services/nova/json/servers_client.py b/tempest/services/nova/json/servers_client.py
index 031259f..b4ea973 100644
--- a/tempest/services/nova/json/servers_client.py
+++ b/tempest/services/nova/json/servers_client.py
@@ -147,8 +147,8 @@
             timed_out = int(time.time()) - start >= self.build_timeout
 
             if server_status != status and timed_out:
-                message = 'Server %s failed to reach %s status within the \
-                required time (%s s).' % (server_id, status,
+                message = 'Server %s failed to reach %s status within the '\
+                'required time (%s s).' % (server_id, status,
                                           self.build_timeout)
                 message += ' Current status: %s.' % server_status
                 raise exceptions.TimeoutException(message)