1. dns resolver should be global unique so dns cache can work. avoid dns query influence hole punching.
2. when system dns failed, fallback to hickory dns.
This patch removes Tarpc & Tonic GRPC and implements a customized rpc framework, which can be used by peer rpc and cli interface.
web config server can also use this rpc framework.
moreover, rewrite the public server logic, use ospf route to implement public server based networking. this make public server mesh possible.