Traditionally, ping returned exit code EX_NOHOST if a DNS lookup failed.
That is still the case for the legacy code in the new merged ping, but
not for IPv6 targets, nor when a DNS lookup is performed in order to
determine which version of the tool to invoke.
While here, also make sure that the error message is consistent.
Sponsored by: NetApp, Inc.
Sponsored by: Klara, Inc.