TUN-3890: Code coverage for cloudflared in CI

Also changed the socks test code so that it binds to localhost, so that
we don't get popups saying "would you like to allow socks.test to use
the network"

hello/hello_test.go

@@ -27,7 +27,7 @@ func TestCreateTLSListenerOnlyHostSuccess(t *testing.T) {
 }
 
 func TestCreateTLSListenerOnlyPortSuccess(t *testing.T) {
-	listener, err := CreateTLSListener(":8888")
+	listener, err := CreateTLSListener("localhost:8888")
 	if err != nil {
 		t.Fatal(err)
 	}