Added import time to IPython/parallel/apps/launcher.py

In a recent commit time.sleep(self.delay) was added to
LocalEngineSetLauncher.start() and SSHEngineSetLauncher.start()
but time was never imported causing ipcluster and anything that
calls the engine launcher to fail. Added the import line

IPython/parallel/apps/launcher.py

@@ -24,6 +24,7 b' import logging'
 import os
 import re
 import stat
+import time
 
 # signal imports, handling various platforms, versions