Gatherer unreachable from outside localhost if --splitter_hostname=localhost is used

[Juan Álvaro Muñoz Naranjo]

When running the gatherer the --splitter_hostname argument should never be set to "localhost", the reason being that peers outside localhost will receive 127.0.0.1 as the gatherer's IP, thus making the gatherer unreachable to them. The "external" IP should be used.

No changes in the code are needed, though a check could be performed at the beginning of gatherer.py.

[Vicente González Ruiz (vicente-gonzalez-ruiz)]

Fixed.