Add an error message if we receive a non-hostname-based dest

This is more helpful than an unwrap and at least points users at the right location.
Upstream issue is https://github.com/briansmith/webpki/issues/54

actix-connect/tests/test_connect.rs

@@ -42,6 +42,7 @@ fn test_rustls_string() {
     let con = test::call_service(&mut conn, addr.into());
     assert_eq!(con.peer_addr().unwrap(), srv.addr());
 }
+
 #[test]
 fn test_static_str() {
     let srv = TestServer::with(|| {