Fix hang when Websocket Read is interrupted

Updated to catch the quit signal and break out of the loop. Tested that ^C shutsdown `btcwallet` as expected, with the same env in which it was hanging earlier.
This select statement currently only has one channel operation, when it should also be selecting on a read of the quit chan.  Yes, this was just done above, but we do that because we want to give the quit chan a higher priority.