RFR 8202608: CommonSeeder test needs a white-box testing mechanism to replace the default entropy source

[Weijun Wang]

Please take a review at

   http://cr.openjdk.java.net/~weijun/8202608/webrev.00/

I added a patched SeedGenerator and remove the reflection calls.

A comment in AbstractDrbg.java removed. That's not a trusted application, it's 
evil.

Thanks
Max