RFR: JDK-8268133 : Update java/net/Authenticator tests to eliminate dependency on sun.net.www.MessageHeader and some other internal APIs

[Mahendra Chhipa]

…ency on sun.net.www.MessageHeader and

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Commit messages:
 - JDK-8268133 : Update java/net/Authenticator tests to eliminate dependency on sun.net.www.MessageHeader and

Changes: https://git.openjdk.java.net/jdk/pull/4317/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4317&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268133
  Stats: 321 lines in 6 files changed: 133 ins; 19 del; 169 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4317.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4317/head:pull/4317

PR: https://git.openjdk.java.net/jdk/pull/4317