RATIS-2125. javadoc jars should not include non-doc items

[adoroszlai]

What changes were proposed in this pull request?

Ratis build generates javadoc when using -Prelease. The javadoc jars have unexpected content, e.g. other jars, classes dir (with all .class files), etc.

Steps to reproduce:

mvn -DskipTests -Prelease clean package
unzip -d before ratis-server-api/target/ratis-server-api-3.2.0-SNAPSHOT-javadoc.jar
ls -1sh before

The problem happens because outputDirectory is set to project.build.directory, which is target/. This directory is also where Maven build puts other items, which then get included in the javadoc jar.

The default location in maven-javadoc-plugin is target/apidocs, we can use that.

https://issues.apache.org/jira/browse/RATIS-2125

How was this patch tested?

Steps described in repro, but using after as directory.

Result:

$ diff -r before/ after/
Only in before: classes
Only in before: generated-sources
Only in before: javadoc-bundle-options
Only in before: maven-archiver
Only in before: maven-javadoc-plugin-stale-data.txt
Only in before: maven-shared-archive-resources
Only in before: .plxarc
Only in before: ratis-server-api-3.2.0-SNAPSHOT.jar
Only in before: ratis-server-api-3.2.0-SNAPSHOT-sources.jar
Only in before: ratis-server-api-3.2.0-SNAPSHOT-tests.jar
Only in before: rat.txt
Only in before: test-classes

[adoroszlai]

Reproducibility check for javadoc works on Java 8, but fails with newer Java. The problem is in the search index JSON files. So it's reverted for now.