RFR 8058715: stability issues when being launched as an embedded JVM via JNI

[david buck]

Hi!

This is a request for code review of my fix for jdk8058715

BUGURL: https://bugs.openjdk.java.net/browse/JDK-8058715
WEBREV: http://cr.openjdk.java.net/~dbuck/8058715/webrev.01/

We have also received confirmation from the original reporter of the 
issue that this solution resolves the crashes they were seeing in their 
environment. I have tested that this change does not break the original 
NX bug workaround. I also ran the NX bug reproducer (v8 benchmark of 
Nashorn running in a loop) using a fastdebug build with the 
-XX:NativeMemoryTracking=summary option. Obviously no crashes or other 
issues were detected.

Cheers,
-Buck