Switch to disable external ip address

[geoffreywiseman]

AWSWL will make calls to api.ipify.org to get the current ip address. If you don't need/want those requests, it will slow down --list a little and make network requests that you might prefer not to make. Add a switch to disable this, like --disable-exip

If I did have a switch, I'd have to print an error if --disable-exip and --add-current or --remove-current were used together, but that's not so hard.