[SPARK-3677] [BUILD] [YARN] pom.xml and SparkBuild.scala are wrong : Scalastyle is never applied to the sources under yarn/common

When we run "sbt -Pyarn scalastyle" or "mvn package", scalastyle is not applied to the sources under yarn/common.
Really? yarn/common/src/main/scala/org/apache/spark/deploy/yarn/ClientArguments.scala has 100+ length line but "sbt/sbt -Pyarn -Phadoop-2.2 scalastyle" couldn't verified.

I think, all projects except for yarn has source directory line <project name>/src but yarn project has source directory yarn/common/src instead of yarn/src so I thought scalastyle couldn't verify.

How do you think?