RFR: 8273670: Remove weak etypes from default krb5 etype list

[Weijun Wang]

This code change removes weak etypes from the default list so it's safer to enable one of them. See the corresponding CSR at https://bugs.openjdk.java.net/browse/JDK-8274207 for more explanation. BTW, please review the CSR as well.

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Commit messages:
 - 8273670: Remove weak etypes from default krb5 etype list

Changes: https://git.openjdk.java.net/jdk/pull/5654/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5654&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273670
  Stats: 186 lines in 7 files changed: 86 ins; 61 del; 39 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5654.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5654/head:pull/5654

PR: https://git.openjdk.java.net/jdk/pull/5654