RFR: 8280016: gc/g1/TestShrinkAuxiliaryData30 test fails on large machines

[Aleksey Shipilev]

See the bug for more details. I would prefer to test the upper boundary for current `G1ConcRSLogCacheSize`.

Additional testing: 
  - [x] Affected/amended test starts to pass

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

Commit messages:
 - Fix

Changes: https://git.openjdk.java.net/jdk/pull/7082/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7082&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8280016
  Stats: 92 lines in 2 files changed: 46 ins; 46 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7082.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7082/head:pull/7082

PR: https://git.openjdk.java.net/jdk/pull/7082