RFR (S): 8219685: Startup failure: assert(!Universe::is_module_initialized()) failed: Incorrect java.lang.Module pre module system initialization

[David Holmes]

bug: https://bugs.openjdk.java.net/browse/JDK-8219685
webrev: http://cr.openjdk.java.net/~dholmes/8219685/webrev/

As per the bug report the assertion is incorrect as the compiler thread 
can be racing against module system initialization in the main thread.

Thanks,
David

PS. I'm away for a few days - reviews in-asbsentia appreciated :)