Debugger: Clean up GdbEngine member data on finish

Restarting with cached outdated information is problematic.

Change-Id: I396da2fef96a161c1ab150134b8e65a758a16d58
Task-number: QTCREATORBUG-16355
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/debugger/gdb/gdbengine.cpp

@@ -4300,6 +4300,14 @@ void GdbEngine::notifyInferiorSetupFailed()
     DebuggerEngine::notifyInferiorSetupFailed();
 }
 
+void GdbEngine::prepareForRestart()
+{
+    m_rerunPending = false;
+    m_commandsDoneCallback = 0;
+    m_commandForToken.clear();
+    m_flagsForToken.clear();
+}
+
 void GdbEngine::handleInferiorPrepared()
 {
     const DebuggerRunParameters &rp = runParameters();