Part 1 of plural ports: Add protocol to Endpoints

This makes it easier to make the second step, which is moving endpoints
to a struct instead of a string.

pkg/api/v1beta3/defaults.go

@@ -80,5 +80,10 @@ func init() {
 				obj.Type = SecretTypeOpaque
 			}
 		},
+		func(obj *Endpoints) {
+			if obj.Protocol == "" {
+				obj.Protocol = "TCP"
+			}
+		},
 	)
 }