Debugger: Add missing state cases in quitDebugger

* Aborting a core dump debugging is a valid state
* Do not try to abort more than once (happens on shutdown)

Change-Id: I075409b3fa1231420fcd72706b18eaa0383fd4f2
Reviewed-by: hjk <hjk@qt.io>

src/plugins/debugger/debuggerengine.cpp

@@ -1352,6 +1352,7 @@ void DebuggerEngine::quitDebugger()
     switch (state()) {
     case InferiorStopOk:
     case InferiorStopFailed:
+    case InferiorUnrunnable:
         d->queueShutdownInferior();
         break;
     case InferiorRunOk:
@@ -1368,6 +1369,7 @@ void DebuggerEngine::quitDebugger()
         notifyEngineRunFailed();
         break;
     case EngineShutdownRequested:
+    case InferiorShutdownRequested:
         break;
     case EngineRunFailed:
     case DebuggerFinished: