[Nestmates] 8196774: [Nestmates] Restore private Lookup check in VerifAccess.isMemberAccessible

[David Holmes]

webrev: http://cr.openjdk.java.net/~dholmes/8196774/webrev/
bug: https://bugs.openjdk.java.net/browse/JDK-8196774

In JDK-8195826 I mistakenly "optimised" the self-check in 
VerifyAccess.isMemberAccessible by removing the check for "private 
Lookup" - thinking class A can access any member of class A. But I 
missed the point that this is a Lookup instance that might have 
restricted Lookup capability - ie public only - in which case access to 
private members must be rejected. The check for "private Lookup" 
capability is critically important.

Thanks,
David