Use correct service type for DNSServiceQueryRecord

Use of ServiceType.A6 (which deprecated) makes following
Native.DNSServiceProcessResult call block.

https://developer.apple.com/library/mac/documentation/Networking/Reference/DNSServiceDiscovery_CRef/Reference/reference.html#//apple_ref/doc/uid/TP40002994-CHdnssdhConstants-SW14
Merge pull request #8 from yanhkim/ipv6_service_type

Use correct service type for DNSServiceQueryRecord