Fix bypass to file blacklist

First commit fixes https://github.com/owncloud/security-tracker/issues/26
I made the method names more clear and corrected the usage as @icewind1991 suggesten in an email.

As a bonus, the second commit suppresses rename hooks for partial files, see https://github.com/owncloud/mirall/issues/331

@icewind1991 @LukasReschke @MTGap please review