Fix and improve connection test for new account creation

When entering the URL in the "new account" in the Drive client GUI, I mispelled the protocol: instead of https://..., I wrote httos://... and hit the "Enter" key which triggered the Connection test.

The GUi then remained spinning and no way to interrupt it spinning, except canceling the window and opening another one and launching the procedure with the right URL again.

To improve this, maybe the code could check at least the protocol is a supported one and decrease the timeout, or provide a way to interrupt the connection attempt.