objects md5-collisions

This patch identifies md5 collisions on objects and sends a 403
from the object server.

Credits for originating this fix are to Michael Factor.

Change-Id: I4f1b32183e2be6bbea56eaff86b9a4c7f440804a
Fix: Bug #1157454
Merge branch 'master' into object-replicator-ssync

Conflicts:
	swift/obj/server.py

Change-Id: I78eb0bae5d19e8a4dbf86765812a47d09be35bc5
PEP8 Fix

Change-Id: I71763af0bb6a220c5696120bedf55146877393fa