wait for seaf-daemon to quit and remove the related warnings

- allow 50ms plus 10ms for `ccnet` and `seaf-daemon` to quit before sending `TERM` signal
- don't print the silly warnings like
```
[12/26/2014 16:14:39]QProcess: Destroyed while process is still running.
[12/26/2014 16:14:39]QProcess: Destroyed while process is still running.
```
Oh, yeah. the issue looks like more interesting as expected. the entire routine looks like:
1. create seafApplet
1. start ccnet/daemon from daemon_mgr
1. start qeventloop from qApp.exe()
1. ...
1. call `QCoreApplication::exit`
1. send aboutToQuit signal to all slots
1. clean up and quite qeventloop
1. destroy seafApplet and daemon_mgr from scope
1. return from function main

I will update the patch soon.