RFR [8]: Excess barriers before JNI accesses, already covered by "Move barriers into typeArrayOop.hpp direct memory accessors"

[Aleksey Shipilev]

http://cr.openjdk.java.net/~shade/shenandoah/8u-jni-barriers/webrev.01/

Found this while cross-referencing integration repo and sh/jdk8u. It seems to me these barriers are
excessive, because they would be all redone when doing typeArrayOop::*_at_addr accessor. This is
partially done by our previous change:
  http://hg.openjdk.java.net/shenandoah/jdk8u/hotspot/rev/a8d83c1c5fce

...and the patch above seems to complete it.

Testing: tier3_gc_shenandoah {fastdebug|release}

Thanks,
-Aleksey