[jdk11u-dev] RFR: 8163921: HttpURLConnection default Accept header is malformed according to HTTP/1.1 RFC

[Amos Shi]

Backport of [JDK-8163921](https://bugs.openjdk.org/browse/JDK-8163921)

Testing
- Local: Test passed
  - `B8185898.java`: Test results: passed: 1
- Pipeline: 
- Testing Machine:

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Commit messages:
 - Backport 28796cbd1d15de678b80295418f5d1f9f59176a6

Changes: https://git.openjdk.org/jdk11u-dev/pull/2645/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2645&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8163921
  Stats: 11 lines in 2 files changed: 0 ins; 1 del; 10 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2645.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2645/head:pull/2645

PR: https://git.openjdk.org/jdk11u-dev/pull/2645