RFR: 7904104: intermittent test failure in TimeoutDefaultSecondsWaiter

[Vladimir Petko]

`victim.interrupt()` is not needed if the process exits  after the kill signal. 
This PR only calls interrupt() if the process fails to exit or the wait is interrupted for some reason. 

This allows TimeoutDefaultSecondsWaiter tests to pass. 

Alternative: update assertion in TimeoutDefaultSecondsWaiter test.

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Commit messages:
 - chore: remove whitespace
 - fix: interrupt the main thread if the process fails to exit
 - fix: do not interrupt the main thread

Changes: https://git.openjdk.org/jtreg/pull/296/files
  Webrev: https://webrevs.openjdk.org/?repo=jtreg&pr=296&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7904104
  Stats: 11 lines in 1 file changed: 8 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jtreg/pull/296.diff
  Fetch: git fetch https://git.openjdk.org/jtreg.git pull/296/head:pull/296

PR: https://git.openjdk.org/jtreg/pull/296