debugger: fix problem where a manual 'continue' was needed after start up.

The problem was that the 'emptyness' of m_cookieForToken was used as an
indication that there was no response packet still in the air. However,
this hash was not reset after a debugging session was aborted using S-F5,
so it could contain items from a previous run, effectively preventing
automatic triggering of the necessary 'continue'.

src/plugins/debugger/gdb/gdbengine.cpp

@@ -198,6 +198,7 @@ void GdbEngine::initializeVariables()
     m_autoContinue = false;
     m_waitingForFirstBreakpointToBeHit = false;
     m_commandsToRunOnTemporaryBreak.clear();
+    m_cookieForToken.clear();
 }
 
 void GdbEngine::gdbProcError(QProcess::ProcessError error)
@@ -1361,6 +1362,10 @@ int GdbEngine::currentFrame() const
 
 bool GdbEngine::startDebugger(const QSharedPointer<DebuggerStartParameters> &sp)
 {
+    // This should be set by the constructor or in exitDebugger().
+    QTC_ASSERT(m_debuggingHelperState == DebuggingHelperUninitialized,
+        initializeVariables());
+
     debugMessage(DebuggerSettings::instance()->dump());
     QStringList gdbArgs;