Remove nfs4_check_deleg_recall().  Move its checks into __setlease() via two
new lock_manager callbacks, fl_mylease and fl_change, so that all leases (not
just NFSv4 lease as with nfs4_check_deleg_recall) are checked.  Default
implementations of fl_mylease and fl_change are provided for the sake of the
fcntl_setlease interface.  Both callbacks must always be defined.

fl_mylease: 

   for the NFSv4 server, this check is used to see if an existing lease
   comes from the same client.  For the fcntl_setlease interface, the existing
   logic is preserved.  the fl_mylease check sees if the existing lease is
   from the input filp.

fl_change: called if the fl_mylease returns true

   the NFSv4 server does not hand out a delegation to a client that already
   has one.  -EAGAIN is returned.  Otherwise lease_modify is used.  For the
   fcntl_setlease interface, the exisiting logic is preserved: The callback
   used in lease_modify().
Signed-off-by: Andy Adamson <andros@citi.umich.edu>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>