MB-10476: Use cb_assert instead of assert

Change-Id: I9adcdbb54430d9d114109c91494670096f2fcb94
Reviewed-on: http://review.couchbase.org/34578
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>