RFR: 6572: Make mbean functions protected by permission checks

[Jessye Coleman-Shapiro]

This patch adds a permission check to Agent MBean functions for the 'control' management permission. 

I have also added a test "testPermissionChecks" to see if a security exception is fired when this permission is not given.

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Commits:
 - 0e3ebef1: Make mbean functions protected by permission checks

Changes: https://git.openjdk.java.net/jmc/pull/39/files
 Webrev: https://webrevs.openjdk.java.net/jmc/39/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JMC-6572
  Stats: 136 lines in 5 files changed: 128 ins; 6 del; 2 mod
  Patch: https://git.openjdk.java.net/jmc/pull/39.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/39/head:pull/39

PR: https://git.openjdk.java.net/jmc/pull/39