java.security: update java.security.KeyStore to jdk8u60

Pulling upstream changes from OpenJDK version jdk8u60 for
java.security.KeyStore.

- New method getAttributes in KeyStore.Entry
- New interface Attribute in KeyStore.Entry
- New constructor specifying protection algorithm and protection parameters in
KeyStore.PasswordProtection.
- New getters for protection algorithm and protection parameters in
KeyStore.PasswordProtection
- In PrivateKeyEntry, SecretKeyEntry and TrustedCertificateEntry, new
constructor allowing to specify attributes, and corresponding getter
getAttributes.

This commit also contains cosmetic JavaDoc changes like
- Use of @code in place of <code> tags.
- Tidied up casts/generics.

This completes the port to jdk8u60 for this class.

Change-Id: Ifec9d07b8f6c367a6fa2672fd5c43747057336ad
Test: make droid docs, vogar KS*{Entry,Password}*.java
Bug: 29631070