Fix deadlock
Merge pull request #921 from egbertbouman/deadlock_fix

Fix deadlock
Merge remote-tracking branch 'upstream/next' into devel_merge_next

Conflicts:
	Tribler/Core/Libtorrent/LibtorrentMgr.py
Merge pull request #966 from LipuFei/devel_merge_next

merge devel and next