Stop publishing test JAR

[ovadiagal]

• The test module was being deployed to when it shouldn't be:

[INFO] Uploading to sonatype-nexus-staging: https://ossrh-staging-api.central.sonatype.com:443/service/local/staging/deployByRepositoryId/io.envoyproxy--ef45b1d1-2f11-422e-80a5-aa5530ef9335/io/envoyproxy/controlplane/test/0.1.50/test-0.1.50.jar

• The empty module that was being deployed was uploading an empty JAR. I'm inclined to believe that this is also the cause of the 400 bad request response from Sonatype:

[INFO] --- jar:3.3.0:jar (default-jar) @ test ---
[WARNING] JAR will be empty - no content was marked for inclusion!
[INFO] 

• Added skipNexusStagingDeployMojo=true to the test module, which gets respected (stack overflow of someone describing the exact same setup + symptoms)