Change seunshare to send kill signals to the childs session.
    Also add signal handler to catch sigint, so if user enters ctrl-C sandbox will shutdown.
    Add -k qualifier to seunshare to have it attempt to kill all processes with
    the matching MCS label.
    Add -C option to sandbox and seunshare to maintain capabilities, otherwise
    the bounding set will be dropped.
    Change --cgroups short name -c rather then -C for consistancy
    Fix memory and fd leaks in seunshare