RFR(xs) 8196121 runtime/appcds/ClassLoaderTest.java fails silently

[Ioi Lam]

Please review a very simple fix:

https://bugs.openjdk.java.net/browse/JDK-8196121
http://cr.openjdk.java.net/~iklam/jdk11/8196121-appcds-class-loader-test-fails-silently.v01/

Cause: the test was archiving the Hello class, but tried to assert that
        this class must not be archived.

Fix:   flip the assertion

Also some clean up:

[1] Use the new TestCommon.run(...).assertNormalExit() API
     to make code more maintainable.
[2] Explicitly check the bootloader of the HelloWB class instead of
     relying on -Xlog:class+load


Thanks
- Ioi