hostip.c: fix leak of addrinfo

hostip.c: fix leak of addrinfo

When creating a dns entry, the addrinfo is passed into the entry on
success and needed deallocation by the caller on failure.

Change the signature to have Curl_dnscache_mk_entry() *always* take
ownership of the addrinfo, even on failure. Change parameter to address
of pointer so that call always clears it.

This makes the handling of failures to Curl_dnscache_mk_entry() simpler.

Fixes #20465
Closes #20468