BIGTOP-2377 has moved Hadoop component to 2.7.2, however all maven test artifacts are still at 2.6.0. Let's fix it
Update to Hadoop 2.7.2
Ideally, we need to find a way for pom versions to be in sync with BOM file, which should be easier now, considering that we have gradle-based build. For this, this will do.
A trivial change, just pushed it into the master.