RFR: Traversal needs to enqueue evacuated oops in codecahe

[Zhengyu Gu]

Webrev: 
http://cr.openjdk.java.net/~zgu/shenandoah/traversal_enqueue_codecache_oops/webrev.00/

Test:

   tier3_gc_shenandoah (fastdebug and release) with
   -XX:+UnlockExperimentalVMOptions
   -XX:-UseDynamicNumberOfCompilerThreads

to avoid the noise from upstream bug [1]

[1] https://bugs.openjdk.java.net/browse/JDK-8209670

Thanks,

-Zhengyu