RFR: 8268131: 2 java/foreign tests timed out

[Maurizio Cimadamore]

This patch increases time out for both TestUpcall and TestDowncall. These tests were already long-running, but with JEP-412, they were beefed up even more, so now they time out on some debug builds.

This patch also address a minor issue in TestResourceScope which can sometimes lead to intermittent failure, depending on how threads are scheduled.

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Commit messages:
 - * Increase timeout for TestUpcall/Downcall

Changes: https://git.openjdk.java.net/jdk/pull/4321/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4321&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268131
  Stats: 10 lines in 3 files changed: 7 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4321.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4321/head:pull/4321

PR: https://git.openjdk.java.net/jdk/pull/4321