pnfsmanager: Addresses compatibility issue with pre 2.6 pools

Address a compatibility issue that prevents the use of the 'rh restore' command
in pre 2.6 pools when used with a 2.6 pnfsmanager.

Target: 2.6
Require-notes: yes
Require-book: no
Patch: http://rb.dcache.org/r/5679/
Acked-by: Albert Rossi <arossi@fnal.gov>