allow lxcapi_get_cgroup_item() on lxc-execute containers

Containers started with lxc-execute may not have a conf, but
nothing in the implementation of lxcapi_get_cgroup_item()
actually needs/uses it, and it can be useful to get items out
of the containers' cgroup items.

Signed-off-by: Dwight Engen <dwight.engen@oracle.com>
Acked-by: Stéphane Graber <stgraber@ubuntu.com>

src/lxc/lxccontainer.c

@@ -1977,7 +1977,7 @@ static int lxcapi_get_cgroup_item(struct lxc_container *c, const char *subsys, c
 {
 	int ret;
 
-	if (!c || !c->lxc_conf)
+	if (!c)
 		return -1;
 
 	if (is_stopped(c))