negotiate: don't advertise datatype if LCB_COMPRESSION_NONE

Have the server inflate the contents

Change-Id: Ifb97b8869e6ae948ae0eca1b4b2f8fb698680dc9
Reviewed-on: http://review.couchbase.org/38091
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>