Disconnect from the WinDebugInterface instance, because every new
run control started will emit the same 'cannotRetrieveDebugOutput()'
signal again.

Change-Id: I94d591e0fa1664f7f7ca0ed4b1d9e021d23cd3e3
Task-number: QTCREATORBUG-5443
Reviewed-on: http://codereview.qt.nokia.com/2327


Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Tobias Hunger <tobias.hunger@nokia.com>