Ensure that the full tendermint commit phase has finished (including

recheckTxs) before allowing the Transactor to query transactions from
the mempool again. This ensures SequentialSigningAccount will always
retrieve the freshest sequence numbers since it will block until all
transactions in the mempool have been replayed to CheckTx after a
commit.

Signed-off-by: Silas Davis <silas@monax.io>