Remove extra vendor field from cartridge name

This PR changes output of `rhc cartridge-list` as follows:
```diff
- jboss-jboss-unified-push-1.0.1 (!) JBoss Unified Push Server 1.0.0.Beta1   web
+ jboss-unified-push-1.0.1 (!) JBoss Unified Push Server 1.0.1.Beta1   web
```