RFR: 8209935: Test to cover CodeSource.getCodeSigners()

[Sibabrata Sahoo]

A Test updated to cover the getCodeSigners.

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Commit messages:
 - Update Implies.java
 - 8209935: Test to cover CodeSource.getCodeSigners()

Changes: https://git.openjdk.java.net/jdk/pull/8286/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8286&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8209935
  Stats: 12 lines in 1 file changed: 4 ins; 2 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8286.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8286/head:pull/8286

PR: https://git.openjdk.java.net/jdk/pull/8286