RFR: 8287544: Replace uses of StringBuffer with StringBuilder in java.naming

[Andrey Turbanov]

StringBuffer is a legacy synchronized class. StringBuilder is a direct replacement to StringBuffer which generally have better performance.
There are some code that still uses StringBuffer in java.naming which could be migrated to `StringBuilder`.

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Commit messages:
 - [PATCH] Replace uses of StringBuffer with StringBuilder in java.naming

Changes: https://git.openjdk.java.net/jdk/pull/8942/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8942&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287544
  Stats: 10 lines in 2 files changed: 0 ins; 0 del; 10 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8942.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8942/head:pull/8942

PR: https://git.openjdk.java.net/jdk/pull/8942