RFR 8225180: SignedObject with invalid Key not throwing the InvalidKeyException in Windows

[Weijun Wang]

Oops, forgot to add the bug title in the subject.

> On Jun 11, 2019, at 11:56 AM, Weijun Wang <weijun.wang at oracle.com> wrote:
> 
> Please take a review at
> 
>   https://cr.openjdk.java.net/~weijun/8225180/webrev.00
> 
> I added some extra info into the exception message not realizing it will be a bug. Revert back to previous code.
> 
> Thanks,
> Max
>