spacemanager: Fix typo in property name

Introduces spacemanager.enable.reserve-space-for-non-srm-transfers.

Target: trunk
Request: 2.7
Require-notes: yes
Require-book: yes
Acked-by: Dmitry Litvintsev <litvinse@fnal.gov>
Patch: http://rb.dcache.org/r/6340/
Merge pull request #367 from gbehrmann/fix/2.7/rb6340

spacemanager: Fix typo in property name