MB-100: add logs for debug

Change-Id: Ib7c5d53fcdc2ad76a3bee0bb6c2179722e9fb8f4
Reviewed-on: http://review.couchbase.org/25006
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>