URGENT: RFR: 8199886: gc/cslocker/TestCSLocker.java crashes

[Per Liden]

JDK-8199620 "Support for JNI object pinning" introduced a bug where a 
naked oop was passed across a safepoint (a call to 
GCLocker::lock_critical). This caused GCLocker-related tests in both 
hs-tier1-2 to fail. This patch stores the oop in a Handle before 
crossing the safepoint.

Bug: https://bugs.openjdk.java.net/browse/JDK-8199886
Webrev: http://cr.openjdk.java.net/~pliden/8199886/webrev.0

Testing: Ran affected jtreg tests locally. hs-tier1-2 currently running 
in mach5

/Per