lxc_start: return 1 not -1 on error

So that exit status doesn't show up as 255.

Reported-by: Andrey Khozov <avkhozov@googlemail.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>