test/format stress sanitizer failed with this assertion. This is likely related to the txn id changes in WT-2237.
[1448383590:833830][93906:0x7fc054d52700], t, WT_CURSOR.insert: ../src/lsm/lsm_cursor.c, 1299: F_ISSET(&session->txn, WT_TXN_HAS_ID) && clsm->primary_chunk != NULL && (clsm->primary_chunk->switch_txn == WT_TXN_NONE || WT_TXNID_LE(session->txn.id, clsm->primary_chunk->switch_txn))