[crac] RFR: Stop JMX RMI before checkpoint & restart after restore

[Radim Vansa]

When JMX is exposed over RMI through system properties `com.sun.management.jmxremote.*` the checkpoint would fail; this PR closes all sockets and reopens listening sockets after restore.

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Commit messages:
 - Stop JMX RMI before checkpoint & restart after restore

Changes: https://git.openjdk.org/crac/pull/146/files
 Webrev: https://webrevs.openjdk.org/?repo=crac&pr=146&range=00
  Stats: 225 lines in 6 files changed: 205 ins; 8 del; 12 mod
  Patch: https://git.openjdk.org/crac/pull/146.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/146/head:pull/146

PR: https://git.openjdk.org/crac/pull/146