RFR: CODETOOLS-7902841: JMH: Reflow JMH file locking code

[Aleksey Shipilev]

This was prompted by SonarCloud complaint:
 "Use try-with-resources or close this "RandomAccessFile" in a "finally" clause."

...in Runner::run.

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

Commit messages:
 - CODETOOLS-7902841: JMH: Reflow JMH file locking code

Changes: https://git.openjdk.java.net/jmh/pull/29/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmh&pr=29&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7902841
  Stats: 35 lines in 1 file changed: 10 ins; 17 del; 8 mod
  Patch: https://git.openjdk.java.net/jmh/pull/29.diff
  Fetch: git fetch https://git.openjdk.java.net/jmh pull/29/head:pull/29

PR: https://git.openjdk.java.net/jmh/pull/29