Switch from gRPC localhost to socket

This commit changes the way CLI and grpc-gateway communicates with the
gRPC backend to socket, instead of localhost. Unauthenticated access now
goes on the socket, while the network interface will require API key (in
the future).

utils.go

@@ -156,11 +156,3 @@ func tailNodesToString(nodes []*tailcfg.Node) string {
 func tailMapResponseToString(resp tailcfg.MapResponse) string {
 	return fmt.Sprintf("{ Node: %s, Peers: %s }", resp.Node.Name, tailNodesToString(resp.Peers))
 }
-
-func IsLocalhost(host string) bool {
-	if strings.Contains(host, LOCALHOST_V4) || strings.Contains(host, LOCALHOST_V6) {
-		return true
-	}
-
-	return false
-}