Don't write duplicate log entries after being daemonized

After being daemonized for the propagate and unpropagate operations,
workspace-control would write duplicate log entries. This happens
because we don't remove the old log handler before adding a new one.
We now remove the log handler when we are closing the log file before
forking.

Closes #103.

control/src/python/workspacecontrol/defaults/Common.py

@@ -123,6 +123,7 @@ def close_logfile(self):
             return
         if not self.logfilehandler:
             return
+        self.log.removeHandler(self.logfilehandler)
         self.logfilehandler.close()
         self.logfilehandler = None