Fix error getting class information from Ingress annotations

controllers/nginx/pkg/cmd/controller/nginx.go

@@ -30,6 +30,7 @@ import (
 
 	"github.com/golang/glog"
 	"github.com/mitchellh/mapstructure"
+	"github.com/spf13/pflag"
 
 	"k8s.io/kubernetes/pkg/api"
 
@@ -251,6 +252,11 @@ func (n NGINXController) Info() *ingress.BackendInfo {
 	}
 }
 
+// OverrideFlags customize NGINX controller flags
+func (n NGINXController) OverrideFlags(flags *pflag.FlagSet) {
+	flags.Set("ingress-class", "nginx")
+}
+
 // testTemplate checks if the NGINX configuration inside the byte array is valid
 // running the command "nginx -t" using a temporal file.
 func (n NGINXController) testTemplate(cfg []byte) error {