RFR: 8299112: HashedPasswordFileTest.java and ExceptionTest.java fails with java.lang.NullPointerException

[Kevin Walls]

Exceptions during setup of these tests could leave e.g. JMXConnector cs as null.
But, we call cs.close() during a finally block and fail with an NPE, obscuring the real failure.
We must only call close if this is not null.

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Commit messages:
 - 8299112: HashedPasswordFileTest.java and ExceptionTest.java fails with java.lang.NullPointerException

Changes: https://git.openjdk.org/jdk/pull/11881/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11881&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8299112
  Stats: 18 lines in 2 files changed: 9 ins; 0 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/11881.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11881/head:pull/11881

PR: https://git.openjdk.org/jdk/pull/11881