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/accounts.py

@@ -291,7 +291,6 @@ class SyncableAccount(Account):
                     name = "Folder %s [acc: %s]" % (remotefolder, self),
                     args = (self.name, remoterepos, remotefolder, localrepos,
                             statusrepos, quick))
-                thread.setDaemon(1)
                 thread.start()
                 folderthreads.append(thread)
             # wait for all threads to finish