bitbake/hob: fix cancel button

An accidental logic inversion (aka thinko) had the cancel button only
cancel a build when the user didn't confirm the cancellation (i.e. clicked
no)...

Signed-off-by: Joshua Lock <josh@linux.intel.com>

bitbake/lib/bb/ui/hob.py

@@ -420,7 +420,7 @@ class MainWindow (gtk.Window):
         label.show()
         response = dialog.run()
         dialog.destroy()
-        if not response == gtk.RESPONSE_YES:
+        if response == gtk.RESPONSE_YES:
             self.handler.cancel_build()
         return