qemu-socket: Clean up inet_connect_opts()

Separate the search for a working addrinfo from the code that does
something with it.  Makes for a clearer search loop.

Use a local Error * to simplify resetting the error in the search
loop.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
