RFR: JDK-8312625: Test serviceability/dcmd/vm/TrimLibcHeapTest.java failed: RSS use increased

[Thomas Stuefe]

Trivial patch.

The test just fires `jcmd System.trim_native_heap`, but without preparing any special memory allocation conditions. Typically, we end up firing the command when VM initialization is done, and therefore end up trimming a lot of memory. But once in a blue moon concurrent allocations may be ongoing, so we may not trim anything, or even see increased RSS.

The patch just loosens the success condition to succeed if the trim happened, irregardless of how much memory had been trimmed.

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Commit messages:
 - JDK-8312625-Test-serviceability/dcmd/vm/TrimLibcHeapTest.java-failed-RSS-use-increased

Changes: https://git.openjdk.org/jdk/pull/15009/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15009&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312625
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15009.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15009/head:pull/15009

PR: https://git.openjdk.org/jdk/pull/15009