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/threadutil.py

@@ -28,8 +28,8 @@ from offlineimap.ui import getglobalui
 ######################################################################
 
 def semaphorereset(semaphore, originalstate):
-    """Wait until the semaphore gets back to its original state -- all acquired
-    resources released."""
+    """Block until `semaphore` gets back to its original state, ie all acquired
+    resources have been released."""
     for i in range(originalstate):
         semaphore.acquire()
     # Now release these.