CBQE-0: add more logging to n1ql

Change-Id: I9f0a407c541d3a7e78bb816aac070b778cee1c6f
Reviewed-on: http://review.couchbase.org/42526
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>