fix mvn warnings in odl-neutron-service

fix mvn warnings in odl-neutron-service

[WARNING] Some problems were encountered while building the effective model for org.opendaylight.neutron:odl-neutron-service:feature:0.11.0-SNAPSHOT
[WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: ${project.groupId}:odl-neutron-spi:xml:features -> duplicate declaration of version ${project.version} @ line 66, column 21
[WARNING] 'dependencies.dependency.(groupId:artifactId:type:classifier)' must be unique: ${project.groupId}:odl-neutron-northbound-api:xml:features -> duplicate declaration of version ${project.version} @ line 73, column 21
[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: I907f9df9be4894cf8f901cd0af1671a2c3db2f54
Signed-off-by: Michael Vorburger <vorburger@redhat.com>