Add test for unknown subcommand
Add test for unknown subcommand

Signed-off-by: Xiangxuan Liu <4b7e97b5f582d7e3f5502df31a6215af2a08a85f@rightcapital.com>

michelleN/deployment-manager,adamreese/deployment-manager,bacongobbler/helm,helm/helm,michelleN/deployment-manager,adamreese/helm,adamreese/deployment-manager,helm/helm,adamreese/deployment-manager,bacongobbler/helm,michelleN/deployment-manager,adamreese/deployment-manager,adamreese/deployment-manager,michelleN/deployment-manager,adamreese/helm