RFR: 8286969: Add a new test library API to execute kinit in SecurityTools.java

[Sibabrata Sahoo]

A new API to execute kinit.

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Commit messages:
 - 8286969: Add a new test library API to execute kinit in SecurityTools.java

Changes: https://git.openjdk.java.net/jdk/pull/8775/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8775&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8286969
  Stats: 12 lines in 1 file changed: 12 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8775.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8775/head:pull/8775

PR: https://git.openjdk.java.net/jdk/pull/8775