RFR: 7904040: jcstress: Drop default stress-fork to 1

[Aleksey Shipilev]

With incoming test changes, we have more configurations to run. To keep run time within reasonable bounds, it makes more sense to drop default -fsm to 1. Users could still re-define it to larger values to get more stress out of individual tests.

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Commit messages:
 - Fix

Changes: https://git.openjdk.org/jcstress/pull/170/files
  Webrev: https://webrevs.openjdk.org/?repo=jcstress&pr=170&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7904040
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jcstress/pull/170.diff
  Fetch: git fetch https://git.openjdk.org/jcstress.git pull/170/head:pull/170

PR: https://git.openjdk.org/jcstress/pull/170