fix memory leaks when the client pings
fix memory leaks when the client pings

`QHash::remove` won't call delete on the value,
so you need to call delete operator or deleteLater method on the value

haiwen/seafile-client,daodaoliang/seafile-client,cloudcopy/client,losingle/seafile-client,cloudcopy/client,lucius-feng/seafile-client,daodaoliang/seafile-client,losingle/seafile-client,losingle/seafile-client,lucius-feng/seafile-client,wgaalves/seafile-client,cloudcopy/client,wgaalves/seafile-client,wgaalves/seafile-client,haiwen/seafile-client,daodaoliang/seafile-client,haiwen/seafile-client,daodaoliang/seafile-client,haiwen/seafile-client,wgaalves/seafile-client,cloudcopy/client,lucius-feng/seafile-client,lucius-feng/seafile-client,losingle/seafile-client