RFR: 8290397: LoadLibraryUnload.java failed with "Too few cleared WeakReferences"

[Roger Riggs]

When running with -Xcomp it seems the wait time for GC to  clear references is insufficient.
Extend timeout waiting for GC.

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Commit messages:
 - 8290397: LoadLibraryUnload.java failed with "Too few cleared WeakReferences"

Changes: https://git.openjdk.org/jdk/pull/9545/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9545&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290397
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9545.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9545/head:pull/9545

PR: https://git.openjdk.org/jdk/pull/9545