[15] RFR: 8235956: Remove javaClasses offset tests

[Claes Redestad]

Hi,

in what I believe is "simply" a lingering remnant of hsx, we still test
for the existence of a few choice fields in javaClasses. These tests
can be turned into asserts that initialization has happened.

Bug:    https://bugs.openjdk.java.net/browse/JDK-8235956
Webrev: http://cr.openjdk.java.net/~redestad/8235956/open.00/

Testing: tier1-3

Thanks!

/Claes