srm: Fix request cancellation due to SURL deletion

An srmRm cancels requests on the SURL that is deleted. The code however just
changed the state to CANCELED rather that calling abort and thus for put
requests the put wasn't properly aborted - in particular the upload directory
isn't deleted, resulting in those leaking.

Target: trunk
Require-notes: yes
Require-book: no
Request: 2.9
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/6998/