CCBC-493: Remove HELLO packet handling

This commit disables the HELLO feature as it will be unused in server
3.0 and may reemerge with different semantics in a later
version

Change-Id: I9e9fe25331229fc02cad2538e9050f8c9b15eb3d
Reviewed-on: http://review.couchbase.org/40306
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>