Format failures:
http://build.wiredtiger.com:8080/job/wiredtiger-test-race-condition-stress-sanitizer/27939/console
http://build.wiredtiger.com:8080/job/wiredtiger-test-format-stress-ppc/19511/console
[1540923318:894655][1155:0x7f4e669c1700], t, file:wt, WT_CURSOR.next: __wt_btcur_next, 607: valid == true [1540923318:894691][1155:0x7f4e669c1700], t, file:wt, WT_CURSOR.next: __wt_abort, 30: aborting WiredTiger library [1540922527:883942][18906:0x3fff6f7ff1b0], t, file:wt.wt, WT_CURSOR.prev: __wt_btcur_prev, 561: valid == true [1540922527:883971][18906:0x3fff6f7ff1b0], t, file:wt.wt, WT_CURSOR.prev: __wt_abort, 30: aborting WiredTiger library