smbd:smb2: clarify and comment code treating dh2c blob check.

smbd:smb2: clarify and comment code treating dh2c blob check.

This makes the code that checks for extra create blobs in the
case of the dh2c blob look very similar to the corresponding
(slightly mode complex) code for the dhnc blob.

With this preparation it will be easier and more obvious how
to add proper treatment of the lease request blobs when leases
get implemented.

Signed-off-by: Michael Adam <obnox@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Sat Oct  5 15:56:11 CEST 2013 on sn-devel-104