RFR: 8260520: Avoid getting permissions in JarFileFactory when no SecurityManager installed

[Claes Redestad]

8260520: Avoid getting permissions in JarFileFactory when no SecurityManager installed

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Commit messages:
 - Avoid getting permissions when there's no SM installed

Changes: https://git.openjdk.java.net/jdk/pull/2263/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2263&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8260520
  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2263.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2263/head:pull/2263

PR: https://git.openjdk.java.net/jdk/pull/2263