Fix deletion of tmp/gitlabhq-gitolite* folders in a NFS environment.

Created by: kouno

When working inside of a Vagrant box with NFS enabled, the deletion of a repository in tmp/ doesn't work every time.

It is related to NFS inability to delete a folder if it's still used by a resource (e.g. rm -rf ./folder would leave the folder and a .nfs* file in it). In this case it's the temporary repository which can't be deleted because ga_repo is still using it.

De-allocating ga_repo is not possible (thanks Ruby), but deleting the folder it points to in the first place fixes the issue.

Reference: http://stackoverflow.com/questions/11228079/python-remove-directory-error-file-exists