RFR: 8275721: Name of UTC timezone in a locale changes depending on previous code

[Naoto Sato]

Fixing time zone name provider for CLDR. In some cases, COMPAT's `UTC` display names were incorrectly substituted for CLDR. The reason it worked fine after `zh-Hant-HK` was that by loading names for `zh-Hant-HK`, the names for `zh-Hant` were cached and hit for the following `zh-MO` name retrieval.

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Commit messages:
 - 8275721: Name of UTC timezone in a locale changes depending on previous code

Changes: https://git.openjdk.java.net/jdk/pull/6709/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6709&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275721
  Stats: 87 lines in 2 files changed: 73 ins; 6 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6709.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6709/head:pull/6709

PR: https://git.openjdk.java.net/jdk/pull/6709