Remove HSM cleaner for PNFS

We do not support PNFS.

Target: trunk
Require-notes: no
Require-book: no
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/5600/
Add DelayedCommand base class

The class is suitable for creating annotated commands that can
execute on another thread.

Target: trunk
Require-notes: no
Require-book: no
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/5598/