RFR: 8368518: [s390x] test failure with failed: wrong size of mach node

[Amit Kumar]

Fixes the test failures. Tested tier1 with release and fastdebug vm. 

Moves one comment related to INTPRESSURE, a leftover from previous change.

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Commit messages:
 - test fix

Changes: https://git.openjdk.org/jdk/pull/27465/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27465&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8368518
  Stats: 6 lines in 3 files changed: 1 ins; 3 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/27465.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27465/head:pull/27465

PR: https://git.openjdk.org/jdk/pull/27465