CCBC-431: Replace vbucket_* with lcbvb_* functions

Change-Id: I55e0b9441fff0f96dd828245e20f2b74e72ab349
Reviewed-on: http://review.couchbase.org/38745
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>