RFR: JDK-8264572 reinsert common pool parallelism assignment

[Doug Lea]

This reinserts setting common pool parallelism inadvertently clobbered in JDK-8259800

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Commit messages:
 - Reinsert omitted assignment
 - Reinsert omitted assignment

Changes: https://git.openjdk.java.net/jdk/pull/3324/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3324&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8264572
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3324.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3324/head:pull/3324

PR: https://git.openjdk.java.net/jdk/pull/3324