[jdk17] RFR: 8268433: serviceability/dcmd/framework/VMVersionTest.java fails with Unable to send object throw not established PipeIO Listener Thread connection

[Alex Menkov]

The fix adds check that IOPipe is connected before sending "quit" command

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Commit messages:
 - Added check that IOPipe is connected

Changes: https://git.openjdk.java.net/jdk17/pull/32/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17&pr=32&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268433
  Stats: 5 lines in 1 file changed: 4 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/32.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/32/head:pull/32

PR: https://git.openjdk.java.net/jdk17/pull/32