RFR: 8316771: Krb5.java has not defined messages for all error codes

[Weijun Wang]

Added 4 missing error codes and removed 2 wrong ones.

KRB_AP_ERR_NOREALM claims itself to be "used in setDefaultCreds() in sun.security.krb5.Credentials" but it's no more.

KRB_AP_ERR_GEN_CRED is used in one place but it's a local error and not meant to be embedded in a message. Therefore safe to be removed.

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Commit messages:
 - remove x bits
 - the fix

Changes: https://git.openjdk.org/jdk/pull/15892/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15892&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316771
  Stats: 79 lines in 3 files changed: 72 ins; 3 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/15892.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15892/head:pull/15892

PR: https://git.openjdk.org/jdk/pull/15892