[jdk17] RFR: 8269064: Dropped messages of AsyncLogWriter cause memleak [v2]

[Xin Liu]

> This patch freed c-strs for the dropped messages. Those c-strs are allocated from os::strdup.

Xin Liu has updated the pull request incrementally with one additional commit since the last revision:

  os::free can handle nullptr.

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Changes:
  - all: https://git.openjdk.java.net/jdk17/pull/121/files
  - new: https://git.openjdk.java.net/jdk17/pull/121/files/1adeeecd..7885b41b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk17&pr=121&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk17&pr=121&range=00-01

  Stats: 4 lines in 1 file changed: 0 ins; 3 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/121.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/121/head:pull/121

PR: https://git.openjdk.java.net/jdk17/pull/121