abandontransaction didn't exist until 0.12.0
Did you upgrade after sending your transaction, or were you actually running the very recent 0.12.0 and not the 0.8.3 that you thought you were running?
Furthermore, if he upgrades to/is using 0.13, then he can just right click the transaction in the transaction list and select
Abandon transaction instead of going to the console.
dumprawtransaction 417b1e741a30571bf27138a965864c27d5bb99c617a7b5864a3d3a24c959b928
It's actually
getrawtransaction not
dumprawtransaction