RFR: 6947: Allow executable name to show up in JPS

[Alex Blewitt]

When executing `jps` to view running Java applications, the displayed name
comes from a `sun.java.command` property. This is usually the name of the
Main-Class when executing it with `java` directly, but Eclipse starts the JVM
by using the native calls which bypasses this setting.

By adding a property definition `sun.java.command=JMC` then the application
will show up appropriately in JPS.

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Commit messages:
 - Allow executable name to show up in JPS

Changes: https://git.openjdk.java.net/jmc/pull/137/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=137&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6947
  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jmc/pull/137.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/137/head:pull/137

PR: https://git.openjdk.java.net/jmc/pull/137