RFR: 8274925: Shenandoah: shenandoah/TestAllocHumongousFragment.java test failed on lock rank check

[Zhengyu Gu]

JDK-8273917 lowered MultiArray_lock rank from nonleaf+2 to nonleaf, that results several Shenandoah tests failed on lock rank check.

This patch lowers ShenandoahAllocFailureGC_lock rank by 2 to maintain original order.

Test:

- [x] hotspot_gc_shenandoah

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Commit messages:
 - v0

Changes: https://git.openjdk.java.net/jdk/pull/5865/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5865&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274925
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5865.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5865/head:pull/5865

PR: https://git.openjdk.java.net/jdk/pull/5865