Maven plugin should fail when partially enabled

The maven build plugin defines two additional test types: mvnsite and mvninstall. Currently, users can say they want to enable these tests without also stating they want the maven plugin enabled. This can lead to nonintuitive failures because those tests rely on command line arguments that are only handled by the maven plugin.

This came up in HBASE-20591, because the HBase project was attempting to have parallel test runs to cover unit tests with different dependency options and had 'mvninstall' without 'maven' result in failures due to stomping on the default maven repo.