RFR: 8233454: Test fails with assert(!is_init_completed(), "should only happen during init") after JDK-8229516

[Jie Fu]

Hi all,

JBS:    https://bugs.openjdk.java.net/browse/JDK-8233454
Webrev: http://cr.openjdk.java.net/~jiefu/8233454/webrev.00/

According to the comment [1], the assert seems to miss the case for 
threads attached via JNI.
For more info, please refer to the JBS.

Could you please review it and give me some advice?

Thanks a lot.
Best regards,
Jie

[1] 
http://hg.openjdk.java.net/jdk/jdk/file/2700c409ff10/src/hotspot/share/runtime/thread.hpp#l1249