When creating container, save configuration if rootfs already exists

Commit 6c6892b "fix multithreaded create()" prevented the container
configuration from being saved if the backing store does not need
to be created.

Signed-off-by: David Ward <david.ward@ll.mit.edu>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>

src/lxc/lxccontainer.c

@@ -1302,6 +1302,8 @@ static bool lxcapi_create(struct lxc_container *c, const char *t,
 	if (lxcapi_is_defined(c) && c->lxc_conf->rootfs.path && !tpath) {
 		/* Rootfs already existed, user just wanted to save the
 		 * loaded configuration */
+		if (!c->save_config(c, NULL))
+			ERROR("failed to save starting configuration for %s\n", c->name);
 		ret = true;
 		goto out;
 	}