CBQE-2495: add more debug info

Change-Id: I4e42d3dee90a3b7ef01ae15ecd1eabbd033579fe
Reviewed-on: http://review.couchbase.org/44426
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>