RFR: 8320198: some reference processing tests don't wait long enough for reference processing to complete

[Tom Rodriguez]

This slightly increases the wait for reference processing to complete to accommodate long Xcomp compile times.  Testing is underway.

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Commit messages:
 - 8320198: some reference processing tests don't wait long enough for reference processing to complete

Changes: https://git.openjdk.org/jdk/pull/16956/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16956&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8320198
  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/16956.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16956/head:pull/16956

PR: https://git.openjdk.org/jdk/pull/16956