Various BSD-derived operating systems including macOS and FreeBSD
require that ping6 be used for IPv6 destinations. The "ping" command
does not understand an IPv6 destination.
FreeBSD 13.x and later do handle IPv6 in the regular ping command,
but also retain a ping6 command. We use ping6 on all versions of
FreeBSD.
Fixes https://github.com/tailscale/tailscale/issues/8225
Signed-off-by: Denton Gentry <dgentry@tailscale.com>
399a80785e