RFR: 8187634: keystore.getCertificateAlias(cert) returns original alias, inconsistent with fix of JDK-6483657

[Weijun Wang]

The alias in the keystore is `mapEntry.getKey()`. `entry.getAlias()` is the original friendly name, which is still useful when overwriting or removing an entry.

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Commit messages:
 - the fix

Changes: https://git.openjdk.org/jdk/pull/17037/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17037&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8187634
  Stats: 99 lines in 2 files changed: 97 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/17037.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17037/head:pull/17037

PR: https://git.openjdk.org/jdk/pull/17037