Reset the controller's internal state when disconnecting

This caused problems when disconnecting from the remote device while
an openrequest was pending and if the controller tried to reconnect
immediately afterwards. The pending request queue was blocked forever.

Change-Id: I444d5ac6763b65ec8baf687e0dccec4b28016a6c
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>