The finalName is only for the name of the artifact in the target
folder, but not for the artifact which will be deployed to a repository.
The simple problem you have is that you defined the buildnumber-maven-plugin only in the pluginManagement but not in the build area:
Add the following to your pom file:
<project>
<build>
<pluginManagement>
...
</pluginManagement>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>buildnumber-maven-plugin</artifactId>
</plugin>
</plugins>
...
</build>
</project>
You need to really execute the buildnumber plugin which is not the case.