RFR: JDK-8314883: Java_java_util_prefs_FileSystemPreferences_lockFile0 write result errno in missing case

[Matthias Baesken]

There seems to be a codepath in Java_java_util_prefs_FileSystemPreferences_lockFile0 where the errno is not stored but potentially accessed in the calling Java code.

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

Commit messages:
 - JDK-8314883

Changes: https://git.openjdk.org/jdk/pull/15402/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15402&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314883
  Stats: 3 lines in 1 file changed: 1 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/15402.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15402/head:pull/15402

PR: https://git.openjdk.org/jdk/pull/15402