pnfsmanager: Use pnfsmanager.enable.* for properties that enable features

Changes

pnfsmanager.folding -> pnfsmanager.enable.folding
pnfsmanager.inherit-file-ownership -> pnfsmanager.enable.inherit-file-ownership
pnfsmanager.full-path-permission-check -> pnfsmanager.enable.full-path-permission-check
pnfsmanager.acl -> pnfsmanager.enable.acl

Target: trunk
Require-notes: yes
Require-book: yes
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/5903/