test/run_trial.py: protect run() with __name__

Without this, any import (e.g. when running "automat-visualize") caused the
tests to be run as a side-effect.

src/wormhole/test/run_trial.py

@@ -11,6 +11,6 @@ from __future__ import unicode_literals
 # So use:
 #  "coverage run -m wormhole.test.run_trial ARGS"
 
-from twisted.scripts.trial import run
-
-run()
+if __name__ == "__main__":
+    from twisted.scripts.trial import run
+    run()