[jdk16u] RFR: 8260010: UTF8ZipCoder not thread-safe since JDK-8243469

[Claes Redestad]

Backport of JDK-8260010, applies cleanly.

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Commit messages:
 - 8260010: UTF8ZipCoder not thread-safe since JDK-8243469

Changes: https://git.openjdk.java.net/jdk16u/pull/7/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk16u&pr=7&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8260010
  Stats: 9 lines in 1 file changed: 6 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk16u/pull/7.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16u pull/7/head:pull/7

PR: https://git.openjdk.java.net/jdk16u/pull/7