RFR: 8302358: Behavior of adler32 changes after JDK-8300208

[Sandhya Viswanathan]

This PR fixes the issue in Adler computation on x86_64. The problem was  due to a missing register clear. Also the test is updated to capture the failed test case.

Please review.

Best Regards,
Sandhya

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Commit messages:
 - update test case.
 - 8302358: Behavior of adler32 changes after JDK-8300208

Changes: https://git.openjdk.org/jdk/pull/12581/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12581&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302358
  Stats: 8 lines in 2 files changed: 5 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/12581.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12581/head:pull/12581

PR: https://git.openjdk.org/jdk/pull/12581