RFR: CODETOOLS-7902901: jcstress: Buffer infrastructure socket connections

[Aleksey Shipilev]

Forked VMs perform two socket connections to the harness VM to get the job config and reply with the result. We should buffer those connections to improve performance.

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Commit messages:
 - Buffer network

Changes: https://git.openjdk.java.net/jcstress/pull/33/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jcstress&pr=33&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7902901
  Stats: 51 lines in 2 files changed: 1 ins; 19 del; 31 mod
  Patch: https://git.openjdk.java.net/jcstress/pull/33.diff
  Fetch: git fetch https://git.openjdk.java.net/jcstress pull/33/head:pull/33

PR: https://git.openjdk.java.net/jcstress/pull/33