srm: Improve status messages of put and bring-online requests

Addresses the issue that the description string of srmPrepareToPut
and srmBringOnline replies show the internal SRM scheduler state
rather than the description of the last request transition.

Target: trunk
Require-notes: yes
Require-book: no
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/6150/