And in the process, fix the related confusing error messages from
pinging your own IP or hostname.
Fixes#2803
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This adds an easy and portable way for us to document how to get
your Tailscale IP address.
$ tailscale ip
100.74.70.3
fd7a:115c:a1e0:ab12:4843:cd96:624a:4603
$ tailscale ip -4
100.74.70.3
$ tailscale ip -6
fd7a:115c:a1e0:ab12:4843:cd96:624a:4603
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>