Typo in help, we create services.

The help output of the openshift command contains a typo, as we create services not service.

```
# output/go/bin/openshift kube create service -c examples/test-service.json
F0814 14:34:02.750933 02417 kubecfg.go:219] usage: kubecfg [OPTIONS] create <builds|minions|pods|replicationControllers|services>
# output/go/bin/openshift kube create services -c examples/test-service.json
Name                Labels              Selector            Port
----------          ----------          ----------          ----------
frontend                                name=frontend       9998

# 
```