Merge tag 'keys-preparse-1-20140722' into keys-next

Here are a set of changes that make all but encrypted and trusted keys use
preparsing.  Unfortunately, encrypted and trusted keys incorrectly use the
update op to alter a key, so other changes will need to be made for them.

These changes permit payload parsing when instantiating or updating a key to be
done before locks are taken and to determine the amount of quota that will be
required in advance.  The latter will make it possible to do LRU discard before
any locks are taken.

Signed-off-by: David Howells <dhowells@redhat.com>