Recursively resolve CNAMES
Recursively resolve CNAMES

Previously we used the blocking `Dnssd.query` function which did
this for us; now that we've switched to an asynchronous style we must
do this ourselves here.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@docker.com>

djs55/vpnkit,djs55/vpnkit,djs55/vpnkit