Fixed exp. image removal

The expired version has to be removed before we attempt an upload.
`chown` and `chgrp` should be done separately, to handle partial
failures.
Merge pull request #4 from arax/exp_img_fix

Fixed exp. image removal
New release created with the changes from Boris Parak
Merge branch 'master' of https://github.com/grid-admin/vmcatcher_eventHndlExpl_ON