Only run Hadoop 2.x or Hadoop 1.x integration tests.

Integration tests cannot be run against multiple Hadoop distros
(i.e., hbase-maven-plugins) in the same multi-module maven build.

To run integration tests against Hadoop 2: mvn clean verify
To run integration tests against Hadoop 1: mvn clean verify -Dplatform=hadoop1

KijiMR will be separately compiled and unit tested under both regimes
in all cases.