RFR: 7357: Double-Checked Locking in Agent Plugin code

[Guru Hb]

Trivial Fortify warning fix

-------------

Commit messages:
 - 7357: Double-Checked Locking in Agent Plugin code

Changes: https://git.openjdk.java.net/jmc/pull/282/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=282&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-7357
  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.java.net/jmc/pull/282.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/282/head:pull/282

PR: https://git.openjdk.java.net/jmc/pull/282