testing: only print when in verbose mode; r=sheehan

Saw this line of output when running `run-tests`.

Differential Revision: https://phabricator.services.mozilla.com/D10781

--HG--
extra : moz-landing-system : lando

testing/vcttesting/docker.py

@@ -748,8 +748,9 @@ def run_ansible(self, playbook, repository=None,
                     if not state['State']['Running']:
                         break
 
-                    print('%s> (timeout waiting for output; re-attaching)' %
-                          repository)
+                    if verbose:
+                        print('%s> (timeout waiting for output; re-attaching)' %
+                              repository)
 
                 if state['State']['ExitCode']:
                     # This should arguably be part of the exception.