Make LXC_CLONE_KEEPNAME work

- Passing the LXC_CLONE_KEEPNAME flag to do_lxcapi_clone() was not respected and
  let to unexpected behaviour for e.g. lxc-clone. We wrap
  clear_unexp_config_line() and set_config_item_line() in an appropriate
  if-condition.

Signed-off-by: Christian Brauner <christianvanbrauner@gmail.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>

src/lxc/lxccontainer.c

@@ -2873,12 +2873,15 @@ static struct lxc_container *do_lxcapi_clone(struct lxc_container *c, const char
 	if (ret < 0)
 		goto out;
 
-	clear_unexp_config_line(c2->lxc_conf, "lxc.utsname", false);
 
 	// update utsname
-	if (!set_config_item_locked(c2, "lxc.utsname", newname)) {
-		ERROR("Error setting new hostname");
-		goto out;
+	if (!(flags & LXC_CLONE_KEEPNAME)) {
+		clear_unexp_config_line(c2->lxc_conf, "lxc.utsname", false);
+
+		if (!set_config_item_locked(c2, "lxc.utsname", newname)) {
+			ERROR("Error setting new hostname");
+			goto out;
+		}
 	}
 
 	// copy hooks