There are a lots of strings being handled inside some LXC functions.
They can be moved to g_autofree to avoid declaring a return value to get
proper code cleanups. This commit is changing functions from
lxc_{controller,cgroup,fuse} only.
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>
Signed-off-by: NJulio Faracco <jcfaracco@gmail.com>