srm-client: Report file level errors

Our srm client in many places simply reports a generic error message
rather than the file level message. This patch resolves this by
reporting an error for each failed file.

Target: trunk
Request: 2.11
Request: 2.10
Require-notes: yes
Require-book: yes
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: https://rb.dcache.org/r/7406/
(cherry picked from commit 042531c1fbd45666c41225a4d4e9a082d8f7a455)
Merge pull request #997 from gbehrmann/fix/2.11/rb7406

srm-client: Report file level errors