RFR: 8286259: Password cleanup after KeyStore.PasswordProtection in P11KeyStore

[Hai-May Chao]

Please review the small update for JDK-8286259.

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Commit messages:
 - 8286259: Password cleanup after KeyStore.PasswordProtection in P11KeyStore

Changes: https://git.openjdk.org/jdk/pull/9254/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9254&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8286259
  Stats: 13 lines in 1 file changed: 12 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9254.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9254/head:pull/9254

PR: https://git.openjdk.org/jdk/pull/9254