RFR 8172201 Replace assert of return type in VarHandle.AccessMode with test

[Mandy Chung]

> On Jan 3, 2017, at 5:12 PM, Paul Sandoz <paul.sandoz at oracle.com> wrote:
> 
> Hi,
> 
> Please review the following which removes an assert statement from the constructor of VarHandle.AccessMode and replaces it with a test:
> 
>  http://cr.openjdk.java.net/~psandoz/jdk9/JDK-8172201-vh-accessmode-return-type-assert/webrev/jdk.patch

This looks fine.

Mandy