Honor git-core meaning of receive.denyDeletes allowing tag deletion

receive.denyDeletes parameter refers only to branch:
http://thread.gmane.org/gmane.comp.version-control.git/99746

Bug: 412640
Change-Id: Ief3fa6abc0c9a18ba0a671ff9854432cec480c4f
Merge "Honor git-core meaning of receive.denyDeletes allowing tag deletion"