RFR(S): 8205946: JVM crash after call to ClassLoader::setup_bootstrap_search_path()

[Calvin Cheung]

bug: https://bugs.openjdk.java.net/browse/JDK-8205946

webrev: http://cr.openjdk.java.net/~ccheung/8205946/webrev.00/

The JVM crash could be simulated by renaming/removing the modules file 
under the jdk/lib directory.
The proposed simple fix is to perform a vm_exit_during_initialization().

Ran hs-tier{1,2,3} tests successfully including the new test case.

thanks,
Calvin