RFR: Remove cleaning of ResolvedMethodTable from Safepoint cleaning tasks

[Zhengyu Gu]

Upstream JDK-8206423 (which already arrived to Shenandoah jdk) moved 
cleaning of ResolvedMethodTable to concurrent phase with lock.

We need to remove corresponding cleaning task from Safepoint cleaning 
tasks, or risk of deadlock.

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


Test:

   tier3_gc_shenandoah (fastdebug + release)

Thanks,

-Zhengyu