From: NeilBrown <neilb@cse.unsw.edu.au>

When adding a item to a sunrpc/svc cache that contains kmalloced data it is
usefully to move the malloced data out of the key object into the new cache
object rather than copying (as then we would need to cope with kmalloc
failure and such).  This means modifying the original.

If the kmalloced data forms part of the key, then we must not move the data
out until after the key isn't needed any more.  So this patch moves the
call to "INIT" on a new item (which fills in the key) to *after* the item
has been found (or not), and also makes sure we only call the HASH function
once.

Thanks to "J.  Bruce Fields" <bfields@fieldses.org>

also

 1/ remove unnecessary assignment
 2/ fix comments that lag behind implementation.