[sheepdog] killing sheep is unsafe - sheep: add option to create pid file

[Jens WEBER]

> > can this meet the needs to shutdown the specific node? I don't want to
> > implement a signal handler for TERM, because we don't want worker threads
> > to handle signals as normal.
> 
> What is the problem with that? Can't we use signalfd for a clean implementation?
> 
> The init.d script only known the start parameter of a sheep, so it is unclear 
> to me how to get the node id?
> 
> Also, debian uses 'start-stop-daemon' to start and stop daemons. And that 
> command send signals to stop
> a daemon (see 'man start-stop-daemon')
> 
> - Dietmar
> 
Both collie node kill command and clean implementation of TERM signal would be nice.

For all day use the collie command is more important.

And we can find a way to get the right node id in the init.d script but the use of 'start-stop-daemon' and sending signal stop is the right and clean way to kill a daemon anyway.

Thanks Jens