Quick fix to restore admin delete confirmations.

Tech debt:
This is enough to fix the reported bug, but the
double click protection needs rewriting, and
Rails UJS needs removing and replacing with
something clearer.

This is associated with a move to update jQuery on
admin (currently v1.7.1 from 2011).
Bring d-click protection in line with styleguide.
Don't double-load the double click protection

The click handlers are already live-bound so this
doesn't need to be run twice.  Doing so doubles up
the handlers, breaking the tests.
Merge pull request #968 from alphagov/fix-delete-confirmations

https://www.pivotaltracker.com/story/show/58806842
Merge commit 'ca46da5a04da712ffd2dcfeea61ad36c6a121a76' into HEAD