I have vCloud Director 1.5.0.464915 and Orchestrator appliance 4.2.0 build 507353. I mistakenly installed the vCloud Director 5.1 plugin, and of course it didn't work with the earlier Director version.
I found kb article 2003386 (Uninstalling a plug-in from VMware vCenter Orchestrator) and followed the instructions.
/opt/vmo/app-server/server/vmo/plugins/o11nplugin-vcloud.dar (removed 1 file)
Restarted service and configuration server
No info for configuration files location on appliance in the article
Packages – deleted content with element
Restarted service and configuration server
The result was the Orchestrator Configuration Plug-ins tab shows: