We can set x-versions-location empty to remove this header in API, but
to keep consistent, we should allow x-remove-versions-location too. The
usage is post "x-remove-versions-locaion: x", just like ACL remove
headers.
Fixed: bug #1107592
Change-Id: I1271eec6401d4a0e8c1a7c2d63aeb8dfef00bf6d