RFR: 8293282: LoadLibraryUnloadTest.java fails with "Too few cleared WeakReferences" [v3]

[Roger Riggs]

> Modify the LoadLibraryUnload test to call gc() more a few times, allowing multiple gc cycles to queue the expected refs.
> Short the timeout on each cycle to 10 sec.

Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:

  Remove unused ReferenceQueue for canary WeakReferences.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/10223/files
  - new: https://git.openjdk.org/jdk/pull/10223/files/498273d9..27a28ed2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10223&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10223&range=01-02

  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10223.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10223/head:pull/10223

PR: https://git.openjdk.org/jdk/pull/10223