lxc-start-ephemeral masks process exit code

[Robert Collins]

lxc-start-ephemeral command
e.g. lxc-start-ephemeral run-my-tests

does 'exit 0' after running the command - see handle_container.

This masks the exit code the command provides, and makes rnuning commands via fail in hard to programmatically diagnose ways. ssh, the underlying remote-execution tool used, *does* preserve exit code:
robertc@lifeless-64:~$ ssh -n localhost -- 'exit 1'
robertc@lifeless-64:~$ echo $?
1
robertc@lifeless-64:~$ ssh -n localhost -- 'exit 0'
robertc@lifeless-64:~$ echo $?
0

So it should be very straight forward to capture the exit code and propogate it out of the script. IIRC our prototype versions did this implicitly, and its been lost since.

This bugs affects the robustness of the Launchpad test suite under lxc.