RFR: JDK-8310549: avoid potential leaks in KeystoreImpl.m related to JNU_CHECK_EXCEPTION early returns

[Matthias Baesken]

In src/java.base/macosx/native/libosxsecurity/KeystoreImpl.m there are a few JNU_CHECK_EXCEPTION macro usages that could potentially cause leaks.

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Commit messages:
 - JDK-8310549

Changes: https://git.openjdk.org/jdk/pull/14590/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14590&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310549
  Stats: 6 lines in 1 file changed: 4 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/14590.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14590/head:pull/14590

PR: https://git.openjdk.org/jdk/pull/14590