[Tests] fix a typo in TestNode.assert_start_raises_init_error()
[Tests] fix a typo in TestNode.assert_start_raises_init_error()

Also, use specific exception for testing TestNode initialization failure.

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