In the cargo configuration add:
...
<deployables>
<deployable>
<groupId>${project.groupId}</groupId>
<artifactId>${project.artifactId}</artifactId>
<type>war</type>
<properties>
<context>my-war-artifact</context>
</properties>
</deployable>
</deployables>
I used this currently in combination with the TomEE and the target filename copied into webapps was the name enclosed by the context-tag added by the suffix "war".