CBQE-2415: n1ql update slicing cases

Change-Id: I42fe795dd2399000b0857f3a848e32645757629c
Reviewed-on: http://review.couchbase.org/41601
Reviewed-by: Ketaki Gangal <ketakigangal@gmail.com>
Tested-by: buildbot <build@couchbase.com>