[jdk11u-dev] RFR: 8265100: (fs) WindowsFileStore.hashCode() should read cached hash code once

[Goetz Lindenmaier]

I backport this for parity with 11.0.17-oracle.

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Depends on: https://git.openjdk.org/jdk11u-dev/pull/1137

Commit messages:
 - Backport 3b576ed99d7664ea0fc851e66f9480a6f4638197

Changes: https://git.openjdk.org/jdk11u-dev/pull/1155/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1155&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8265100
  Stats: 5 lines in 1 file changed: 2 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1155.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1155/head:pull/1155

PR: https://git.openjdk.org/jdk11u-dev/pull/1155