libcli/security: Fix integer overflow

libcli/security: Fix integer overflow

On a typical machine where the size of ‘int’ is 32 bits or smaller, a
sub-authority of 2147483649 would be ordered before a sub-authority of
1, even though it is greater.

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>