Make bodge unicorn more explicit

When running `vm.bodge_unicorn:frontend` the script would find both
`datainsight-frontend` and `frontend`.

Given the included `grep` chain already finds things only by the
directory name, I've anchored the grep in directory delimiters to ensure
it only kills exactly the thing we want.
Merge pull request #22 from alphagov/fix-bodge-unicorn

Make bodge unicorn more explicit