add capability to bootstrap from DNS
Add a simple test and mock for genDNS
fix from comments
add apurl checking and logging
Fully resolve DNS entries to IPs and ignore single errors (such as no etcd-server-ssl)
rename flag to discovery-srv
resolve all hostnames in DNS discovery
change logging
Merge pull request #1947 from barakmich/dns_bootstrap

add capability to bootstrap from DNS SRV