RFR: 8225433: Clarify behavior of PKIXParameters.setRevocationEnabled when PKIXRevocationChecker is used

[Sean Mullan]

This change improves the specification for the case when a `PKIXRevocationChecker` is supplied as one of the `CertPathChecker` parameters. Specifically, it makes it more clear that a `PKIXRevocationChecker` overrides the default revocation checking mechanism of a PKIX service provider, and will be used to check revocation irrespective of the setting of the RevocationEnabled parameter.

Will also file a CSR.

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Commit messages:
 - 8225433: Clarify behavior of PKIXParameters.setRevocationEnabled when PKIXRevocationChecker is used

Changes: https://git.openjdk.java.net/jdk/pull/8287/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8287&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8225433
  Stats: 18 lines in 2 files changed: 9 ins; 0 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8287.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8287/head:pull/8287

PR: https://git.openjdk.java.net/jdk/pull/8287