RFR: 8293197: Avoid double racy reads from non-volatile fields in SharedSecrets

[Andrey Turbanov]

After integration of [JDK-8259021](https://bugs.openjdk.org/browse/JDK-8259021) a few more fields were added to `SharedSecrets` class. It make sense to update their reading code to use the same idiom.

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Commit messages:
 - [PATCH] SharedSecrets should avoid double racy reads from non-volatile fields
 - [PATCH] SharedSecrets should avoid double racy reads from non-volatile fields

Changes: https://git.openjdk.org/jdk/pull/10076/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10076&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293197
  Stats: 16 lines in 1 file changed: 8 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/10076.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10076/head:pull/10076

PR: https://git.openjdk.org/jdk/pull/10076