srm: Fix space expiration check in space query

Target: trunk
Require-notes: no
Require-book: no
Request: 2.7
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/6220/
(cherry picked from commit 7782b922864f7ab3332cb21ec4cb289486416ab2)