Using IP address in donor's socat with TLS/SSL and certificate
which doesn't contain IP address in CN or SubjectAltName causes
transfer to fail with message:

socat[5799] E certificate is valid but its commonName does not
match hostname.

This patch tries to reverse resolve IP address to hostname and
use it for transfer. If reverse resolution fails, IP address is
still used as fall-back, so proper A/AAAA and PTR records are
important, but not mandatory.

Certain certificates cannot contain IP addresses, e.g. FreeIPA's
Dogtag doesn't allow it, so in my case I would need to use self-
signed certificates instead, use verify=0 with socat or don't use
TLS/SSL at all. Issue is mentioned in MDEV-9403.