RFR: 8255959: Timeouts in VectorConversion tests

[Martin Doerr]

I'd like to address the remaining timeouts on PPC64. Other ones were resolved by JDK-8256581.

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Commit messages:
 - 8255959: Timeouts in VectorConversion tests

Changes: https://git.openjdk.java.net/jdk/pull/1704/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1704&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255959
  Stats: 11 lines in 1 file changed: 10 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1704.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1704/head:pull/1704

PR: https://git.openjdk.java.net/jdk/pull/1704