RFR: 8252657: JVMTI agent is not unloaded when Agent_OnAttach is failed

[Yasumasa Suenaga]

Hi all,

Please review this change:

  JBS: https://bugs.openjdk.java.net/browse/JDK-8252657
  webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8252657/webrev.00/

I tried to attach JVMTI agent which returns JNI_ERR in Agent_OnUnload via 
JVMTI.agent_load dcmd. I expected the library would be unloaded, but I saw it 
in VM.dynlibs dcmd even though it was failed to load.

Please see JBS how to reproduce.


Thanks,

Yasumasa