Updates the Scala version in the bom. I tested the Kafka and Spark builds with ./gradlew kafka-rpm -Dbuildnodeps=true, ./gradlew spark-rpm -Dbuildnodeps=true. I also tested Phoenix with ./gradlew phoenix-rpm (thus building all the dependencies).
For future reference, note that Spark hard codes the Scala version to 2.10.4 and 2.11.7 (for the scala-2.11 profile). Scala version has no effect on the Spark build.