MB-7509 Removed item should be removed from keyIndex too.

Change-Id: I842be6f77606e99ca7b47a451fd5f03e4b95feb6
Reviewed-on: http://review.couchbase.org/24730
Reviewed-by: Jin Lim <jin@couchbase.com>
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: xiaoqin ma <maxiaoqin2005@gmail.com>