ContainerRegistry doesn't support registry name (path-based)

[hrimhari]

Steps to reproduce:

1. Setup a registry in a Docker registry provider (i.e. JFrog Cloud). The registry will be identified by <provider-host>/<registry-name>. Example: registryprovider.example.com/registryname
2. Specify the fully qualified registry name to -p:ContainerRegistry.

Expected behavior:

• Image is pushed to remote registry.

Actual behavior: Could not recognize registry