RFR 8232008: Shenandoah: C1 load barrier does not match interpreter version

[Zhengyu Gu]

Bug: https://bugs.openjdk.java.net/browse/JDK-8232008
Webrev: http://cr.openjdk.java.net/~zgu/JDK-8232008/webrev.00/

Test:
   hotspot_gc_shenandoah (fastdebug and release) with x86_64 and x86-32 
JVM on Linux.

Thanks,

-Zhengyu