RFR: JDK-8262163: Extend settings printout in jcmd VM.metaspace

[Thomas Stuefe]

This is quite trivial. 

jcmd VM.metaspace prints metaspace settings at the end of its printout. Missing from that printout are some settings which would be nice to see here, eg the GC thresholds and CDS settings (nice to know since CDS affects how metaspace is used).

Example output:

Settings:
MaxMetaspaceSize: 17179869184,00 GB
CompressedClassSpaceSize: 1,00 GB
Initial GC threshold: 20,75 MB
Current GC threshold: 21,50 MB
CDS: on
MetaspaceReclaimPolicy: balanced
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Tests: Manually ran runtime/Metaspace/PrintMetaspaceDcmd.java.

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Commit messages:
 - Start

Changes: https://git.openjdk.java.net/jdk/pull/2686/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2686&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8262163
  Stats: 10 lines in 1 file changed: 10 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2686.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2686/head:pull/2686

PR: https://git.openjdk.java.net/jdk/pull/2686