Fix disconnect button in notification item

The notification item for bitmask android includes a button 'disconnect' when VPN is not active. If you hit this button, it will halt the attempt to connect, although the main panel does not get updated and still shows that it is trying to connect.

This button should be fixed in two ways:

(1) It should say "Cancel" instead of "Disconnect", since disconnect implies that there is an active working connection. (2) When you press it, it should ensure that any connection attempts are halted and that the main panel's UI elements are updated to reflect this.

(from redmine: created on 2014-09-20)