lxc-execute: actually exit with the status of the spawned task
lxc-execute: actually exit with the status of the spawned task

Now that we have things propagated through init and liblxc correctly, at
least in non-daemon mode, we can exit with the actual exit status of the
task, instead of always succeeding, which is not so helpful.

Signed-off-by: Tycho Andersen <6b523322678240882acbb4da5312a12d8cd0082d@tycho.ws>

ss1h2a3tw/lxc,thmo/lxc,hallyn/lxc,hallyn/lxc,ss1h2a3tw/lxc,caglar10ur/lxc,thmo/lxc,caglar10ur/lxc,ss1h2a3tw/lxc,hallyn/lxc,caglar10ur/lxc,thmo/lxc