deployment key resides after repository deletion (BB-5930)

1. Create/import a repository;
2. Add a deployment key (an SSH key for my local linux box);
3. Delete that repository;
4. Add SSH key for account: oops! that key is used as a deployment key!

Quick fix, works if you imported that repo:

1. Re-import the same repository;
2. Add the same deployment key to it;
3. Remove that deployment key;
4. Remove that repo;
5. Whoa, it works now!