artifact: remove duplicated features-neutron-test dependency

artifact: remove duplicated features-neutron-test dependency

eliminate the following warning.

> [WARNING] Some problems were encountered while building the effective model for org.opendaylight.neutron:neutron-artifacts:pom:0.9.0-SNAPSHOT
> [WARNING] 'dependencyManagement.dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: ${project.groupId}:features-neutron-test:xml:features -> duplicate declaration of version ${project.version} @ line 69, column 25
> [WARNING]
> [WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
> [WARNING]
> [WARNING] For this reason, future Maven versions might no longer support building such malformed projects.

Change-Id: I127ee79eae5701a7c1d2f9805171dfa82c317233
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>