library: use getaddrinfo with AI_CANONNAME to find a FQDN
Currently adcli creates service principals only with a short name if the hostname of the client is a short name. This would fail is Kerberos/GSSAPI clients will use the fully-qualified domain name (FQDN) to access the host.
With this patch adcli tries to expand the short name by calling getaddrinfo with the AI_CANONNAME hint.
Related to #1 (closed)