LanguageClient: fix restarting language servers

A timer is used to ensure a server shuts down after a certain amount of
time. This timer needs to be reset after restarting the client
otherwise the client gets forcefully deleted after the timeout.

Change-Id: I804678ec9491328e3da11fd0f9faa59f6e5f7d92
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/languageclient/client.cpp

@@ -1661,6 +1661,7 @@ void Client::setLogTarget(LogTarget target)
 
 void Client::start()
 {
+    d->m_shutdownTimer.stop();
     LanguageClientManager::addClient(this);
     d->m_clientInterface->start();
 }