The current transport client TLS checking will pass an IP address into
VerifyHostnames if there is DNSNames SAN. However, the go runtime will
not resolve the DNS names to match the client IP. Intead, resolve the
names when checking.
pkg/ is a collection of utility packages used by etcd without being specific to etcd itself. A package belongs here
only if it could possibly be moved out into its own repository in the future.