RFR: 8298907: nsk JDI tests pass if the debuggee failed to launch

[Leonid Mesnik]

Updated run() to return exitCode and make testExitCode non-static to don't use it in run()

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Commit messages:
 - fixed cp
 - 8298907: nsk JDI tests pass if the debuggee failed to launch

Changes: https://git.openjdk.org/jdk/pull/12270/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12270&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8298907
  Stats: 367 lines in 186 files changed: 0 ins; 0 del; 367 mod
  Patch: https://git.openjdk.org/jdk/pull/12270.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12270/head:pull/12270

PR: https://git.openjdk.org/jdk/pull/12270