RFR(xs): 8220173: assert(_handle_mark_nesting > 1) failed: memory leak: allocating handle outside HandleMark

[Robbin Ehn]

Hi all, please review.

Issue:
https://bugs.openjdk.java.net/browse/JDK-8220173
Webrev:
http://cr.openjdk.java.net/~rehn/8220173/webrev/

A thread have a pending exception and we try to handleize the oop without a 
HandleMark before the handshake.
The CautiouslyPreserveExceptionMark should only cover the handshake operation 
not the transition, so moved that into proper scope and added HandleMark.

Passes t1.

Thanks Robbin