[NETNS]: Consolidate kernel netlink socket destruction.

Create a specific helper for netlink kernel socket disposal. This just
let the code look better and provides a ground for proper disposal
inside a namespace.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Tested-by: Alexey Dobriyan <adobriyan@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/fs/ecryptfs/netlink.c b/fs/ecryptfs/netlink.c
index 9aa3451..f638a69 100644
--- a/fs/ecryptfs/netlink.c
+++ b/fs/ecryptfs/netlink.c
@@ -237,7 +237,6 @@
  */
 void ecryptfs_release_netlink(void)
 {
-	if (ecryptfs_nl_sock && ecryptfs_nl_sock->sk_socket)
-		sock_release(ecryptfs_nl_sock->sk_socket);
+	netlink_kernel_release(ecryptfs_nl_sock);
 	ecryptfs_nl_sock = NULL;
 }