Add debugging to know which session has a hazard pointer

[1535338740:356623][2153:0x7f355ffff700], file:test2, WT_CURSOR.insert: __wt_hazard_check_assert, 422: hazard pointer reference to discarded object: ((nil): __wt_row_search, line 450)

[1535338740:357616][2153:0x7f355ffff700], file:test2, WT_CURSOR.insert: __split_parent, 875: __wt_hazard_check_assert(session, next_ref, false)

[1535338740:357955][2153:0x7f355ffff700], file:test2, WT_CURSOR.insert: __wt_abort, 30: aborting WiredTiger