io: Fix partial struct copy in qio_dns_resolver_lookup_sync_inet()

io: Fix partial struct copy in qio_dns_resolver_lookup_sync_inet()

Commit aec21d3175 (qapi: Add InetSocketAddress member keep-alive)
introduces the keep-alive flag, but this flag is not copied together
with other options in qio_dns_resolver_lookup_sync_inet().

This patch fixes this issue and also prevents future ones by copying the
entire structure first and only then overriding a few attributes that
need to be different.

Fixes: aec21d31756c (qapi: Add InetSocketAddress member keep-alive)
Signed-off-by: Juraj Marcin <jmarcin@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>