RFR(XS) 8065346 - WB_AddToBootstrapClassLoaderSearch calls JvmtiEnv::create_a_jvmti when not in _thread_in_vm state

[Ioi Lam]

Hi,

Please review a simple fix for whitebox test API:

http://cr.openjdk.java.net/~iklam/8065346-jvmti-test-crash/
     https://bugs.openjdk.java.net/browse/JDK-8065346

Summary of fix:

     The JVMTI calls expect the current thread to be in VM state, but 
JNI GetStringUTFChars
     expects the thread to be in Native state.

     So I moved the ThreadToNativeFromVM constructors accordingly to 
make everyone happy.

Tests:

     I ran the tests with a debug hotspot build and the tests passed 
after the fix.

Thanks
- Ioi