[test] Fix nits leftover from 11771
[test] Fix nits leftover from 11771

Remove unused variable reassignments in p2p_invalid_tx.py and call
send_txs_and_test() with valid transaction.

peercoin/peercoin,DigitalPandacoin/pandacoin,DigitalPandacoin/pandacoin,DigitalPandacoin/pandacoin,DigitalPandacoin/pandacoin,peercoin/peercoin,DigitalPandacoin/pandacoin,peercoin/peercoin,peercoin/peercoin,peercoin/peercoin,DigitalPandacoin/pandacoin,peercoin/peercoin