refs #213 Save a rollback of cursorids created by multi-statement
transactions so we can erase them on txn complete. This guaruntees
the lifetime of client cursors created by an MST is shorter than
the txn itself. Additionally, check that getMore() cursors are
used by the correct transaction stacks and assert otherwise.
Add some tests to verify that MSTs can create multiple cursors, iterate
over them in interleaved order, and also perform interleaved writes.
Revert original cloner fix now that MSTs can interleave cursor/insert
operations.