ping: Simplify protocol selection.

• Interrupt the option loop as soon as we have an indication of which protocol is intended.
• If we end up having to perform a DNS lookup, loop over the entire result looking for either IPv4 or IPv6 addresses.

Sponsored by: NetApp, Inc.
Sponsored by: Klara, Inc.
Reviewed by: rscheff, kevans, allanjude
Differential Revision: https://reviews.freebsd.org/D42137