RFR: 8274205: Handle KDC_ERR_SVC_UNAVAILABLE error code from KDC

[Alexey Bakhtin]

The code change handles KDC_ERR_SVC_UNAVAILABLE error code (29) received from KDC and resends the initial request to the next KDC in the list. It aligns error code handling with the MIT Kerberos implementation.
sun/security/krb5 tests passed

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Commit messages:
 - 8274205: Handle KDC_ERR_SVC_UNAVAILABLE error code from KDC

Changes: https://git.openjdk.java.net/jdk/pull/5658/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5658&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8274205
  Stats: 8 lines in 2 files changed: 6 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5658.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5658/head:pull/5658

PR: https://git.openjdk.java.net/jdk/pull/5658