use quarter-second heartbeat period in IPython.parallel tests

No need for conservative heartbeat period when running local tests, which
directly affects the time it takes to register or remove an engine.

IPython/parallel/tests/__init__.py

@@ -55,7 +55,7 b' def setup():'
     
     cp = TestProcessLauncher()
     cp.cmd_and_args = ipcontroller_cmd_argv + \
-                ['--profile=iptest', '--log-level=50']
+                ['--profile=iptest', '--log-level=50', '--ping=250']
     cp.start()
     launchers.append(cp)
     tic = time.time()