Don't setDaemon explicitly, it's done inherently

All ExitNotifyThreads and InstanceLimitThreads are setDaemon(True) in their
constructor, so there is no need to do that again in the code.

Signed-off-by: Sebastian Spaeth <Sebastian@SSpaeth.de>

offlineimap/init.py

@@ -358,7 +358,6 @@ class OfflineImap:
                                  name='Sync Runner',
                                  kwargs = {'accounts': syncaccounts,
                                            'config': self.config})
-                t.setDaemon(True)
                 t.start()
                 threadutil.exitnotifymonitorloop(threadutil.threadexited)
             self.ui.terminate()