CDB: Use false instead of zero when a boolean is returned

Change-Id: I52e95cd046c49cc1b3e2e433e80a6825042372f3
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
CDB: Make it possible to kill the cdb...

...when the cdb got hung up.

Handle abort like in almost any debugger engine, first kindly
ask to quit. If this doesn't work kill the debugger process.

Task-number: QTCREATORBUG-13173
Change-Id: I1ddc98b1ffe00342c96d104c16099b500e52bc07
Reviewed-by: hjk <hjk121@nokiamail.com>