RFR: 8256278: Shenandoah: Avoid num of dead callback from weak processor in Shenandoah root verifier [v2]

[Zhengyu Gu]

> Shenandoah root verifier currently uses WeakProcessor to verify weak oops, but it always generates report_num_dead callback if registered. This callback fails runtime/stringtable/StringTableCleaningTest.java test with -XX:+ShenandoahVerify.
> 
> Test:
> 
> - [x] hotspot_gc_shenandoah
> - [x] Passed failed test
>        TEST_VM_OPTS="-XX:+UseShenandoahGC -XX:+UnlockDiagnosticVMOptions -XX:-ShenandoahVerify" make 
>        CONF=linux-x86_64-server-release run-test TEST=runtime/stringtable/StringTableCleaningTest.java

Zhengyu Gu has updated the pull request incrementally with one additional commit since the last revision:

  Removed unused header

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1189/files
  - new: https://git.openjdk.java.net/jdk/pull/1189/files/e9821d97..229cbaf7

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1189&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1189&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1189.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1189/head:pull/1189

PR: https://git.openjdk.java.net/jdk/pull/1189