tools: Indicate container startup failure

tools: Indicate container startup failure

When running lxc-autostart we do not currently indicate failure to start
containers, either partial failure i.e. some of the containers failed to
start or total failure i.e. all of the containers failed to start.

Indicate container startup failure.  For total failure exit(1), for
partial failure exit(2).

Signed-off-by: Tobin C. Harding <me@tobin.cc>