RFR: 8220095: Assertion failure when symlink (with different name) is used for lib/modules file

[Ioi Lam]

Hi,

Here's an updated webrev:

http://cr.openjdk.java.net/~iklam/jdk13/8220095_assert_when_lib_modules_is_symblink.v02/

The reported crash was caused by the ClassLoader::is_modules_image() 
API. I've
updated the bug description to analyze all the intended use of this API, 
and the conclusion
is to remove this confusing API and replace it with something simpler.

The alternative is to fix the implementation of this API, but that means 
we have to add lots of
docs to describe how it works, and who should call it. That doesn't seem 
to worth it.

Thanks to Jiangli for the initial analysis and the test case.

- Ioi