RFR: 7903383: jcstress: All State objects should be processed

[Aleksey Shipilev]

There is a reasonable expectation that once `@State` object is created, it would eventually be acted upon. In fact, the Javadoc for `@Actor`/`@Arbiter` mentions that actor methods would be called on each state object exactly once. There are cases where users rely on this implicit lifecycle assumption to perform cleanups at `@Arbiter` methods.

Unfortunately, once jcstress leaves the test, it keeps last created state object slice unprocessed, which breaks this assumption.

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jcstress/pull/124/files
 Webrev: https://webrevs.openjdk.org/?repo=jcstress&pr=124&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7903383
  Stats: 85 lines in 4 files changed: 32 ins; 16 del; 37 mod
  Patch: https://git.openjdk.org/jcstress/pull/124.diff
  Fetch: git fetch https://git.openjdk.org/jcstress pull/124/head:pull/124

PR: https://git.openjdk.org/jcstress/pull/124