Query response without ip address is ignored #124
Description
As the title says, this library expects the mDNS responder to eventually respond DNS-SD query with a record with ip address filled.
However, it seems it's not always the case. Since this library ignores those (incomplete) responses, the library user has no option other than to just wait for better responses for say, minutes.
If we've at least instance name (without ip address) in response to the query, we can use instance name to execute a question.
And as far as I can see, it's a lot faster and more reliable than just waiting for the better query response.
Is that check in client.mainloop() is really needed? Is that doing some good?