mainview: make ambiguous shortcuts activate

For hang up call shortcut, use onActivatedAmbiguously since
we have two existences.

Gitlab: #126
Change-Id: I46167b95212821c88651a06700013aeec38a96a3

src/mainview/MainView.qml

@@ -738,6 +738,7 @@ Window {
         sequence: "Ctrl+D"
         context: Qt.ApplicationShortcut
         onActivated: CallAdapter.hangUpThisCall()
+        onActivatedAmbiguously: CallAdapter.hangUpThisCall()
     }
 
     Shortcut {

src/mainview/components/CallStackView.qml

@@ -36,6 +36,7 @@ Rectangle {
         sequence: "Ctrl+D"
         context: Qt.ApplicationShortcut
         onActivated: CallAdapter.hangUpThisCall()
+        onActivatedAmbiguously: CallAdapter.hangUpThisCall()
     }
 
     // When selected conversation is changed,