Re: [Libvir] [PATCH] lxc: handle SIGCHLD from exiting container

This patch allows the lxc driver to handle SIGCHLD signals from exiting containers. The handling will perform some cleanup such as waiting for the container process and killing/waiting the tty process. This is also required as a first step towards providing some kind of client container exit notification. Additional support is needed for that but this SIGCHLD handling is what would trigger the notification. libvirtd was already catching SIGCHLD although it was just ignoring it. I implemented a mechanism to distribute the signal to any other drivers in the daemon that registered a function to handle them. This required some changes to the way libvirtd was catching signals (to get the pid of the sending process) as well as an addition to the state driver structure. The intent was to provide future drivers access to signals as well.