[jdk11u-dev] RFR: 8270096: Shenandoah: Optimize gc/shenandoah/TestRefprocSanity.java for interpreter mode

[Aleksey Shipilev]

Clean backport to stabilize the test.

Additional testing:
 - [x] Affected test still passes

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

Commit messages:
 - Backport 4f322a9b6c9cfdf080df23326daa45733f1b9aad

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/259/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=259&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8270096
  Stats: 17 lines in 1 file changed: 7 ins; 0 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/259.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/259/head:pull/259

PR: https://git.openjdk.java.net/jdk11u-dev/pull/259