CBQE-0: tuq: add debug info for index queries

Change-Id: Ic5e3cf62204335cf587316ed4c8dc3aa6967d9c2
Reviewed-on: http://review.couchbase.org/33248
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>