[jdk11u-dev] RFR: 8286293: Tests ShortResponseBody and ShortResponseBodyWithRetry should use less resources

[Goetz Lindenmaier]

I backport this test-only change for parity with 11.0.17-oracle.

I did the following adaptions:
ShortResponseBody.java
* Adapt test run specification to requirements of 11.
  This did not match in this file, but all other files
  needed fixes, too.
* Resolve includes
* Removal of four methods did not apply clean.
  The methods were moved to the new files.
  I dropped the old implementation and am using the 
  new ones in the new files except for assertExpectedMessage()
  which is not in 11.

ShortResponseBodyPostWithRetry.java
* test run specification: different context

Tests are compiling and passing.

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Commit messages:
 - Backport f143386109bce2a2e7241f685e2df26849a0ad48

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/1095/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=1095&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286293
  Stats: 505 lines in 5 files changed: 321 ins; 170 del; 14 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/1095.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/1095/head:pull/1095

PR: https://git.openjdk.java.net/jdk11u-dev/pull/1095