Suggested usage:

	return error_log_errno(err, "Failed: %s", "some error");

It sets errno to the value of err, then calls SYSERROR with the format and remaining args.

It always returns -1.
Suggested-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Thomas Parrott <thomas.parrott@canonical.com>