Connection errors when using msrdcex prevent new connections.

## Currently an error connecting to a session prevents additional connections.

### Steps to reproduce.

1. Create an AVD application/desktop with a target executable or host that does not exist.
2. Use msrdcex to connect to that resource.
3. Leave the error window open.
4. Launch msrdcex again with a known working application.

### Current behavior:
The second launch of msrdcex does not attempt to connect until the error box is closed on the first msrdcex instance.

### Expected behavior
The second instance of msrdcex should launch instantly.