Allow users to remove and update redirects from deleted repos (BB-4177)

I can't remove redirect or recreate removed repository at https://bitbucket.org/techtonik/pypi/ - please do this for me, so that it should be possible to clone repository from the new location.

See also the comment - http://confluence.atlassian.com/pages/viewpage.action?pageId=282173855&focusedCommentId=284366372&#comment-284366372