Increased the buffer for netlink responses.

If an error occurs while manipulating policies in the kernel, the
original netlink request gets attached to the response.

Prior to Linux 2.6.32 the size in the netlink header of the response was
wrong.

src/pluto/kernel_netlink.c

@@ -348,6 +348,7 @@ static bool netlink_policy(struct nlmsghdr *hdr, bool enoent_ok,
 	struct {
 		struct nlmsghdr n;
 		struct nlmsgerr e;
+		char data[1024];
 	} rsp;
 	int error;