Fix issue with filtering deployments

Fixes issue: openfaas#736 raised by pkoelbl where all deployments in
the openfaas-fn namespace were being returned via the REST
API when listing functions.

The selector's Add method was generating a new value to be
returned instead of updating itself. A negative test would have
shown this and may be worth adding to the codebase at a
later date, or being mocked/stubbed. A PR would be welcomed
for this.

Thanks also to @LucasRoesler for helping to investigate
and confirm the fix.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <[email protected]>

Author: alexellis

pkg/handlers/reader.go

@@ -66,9 +66,9 @@ func getServiceList(functionNamespace string, deploymentLister v1.DeploymentList
 	if err != nil {
 		return functions, err
 	}
-	sel.Add(*req)
+	onlyFunctions := sel.Add(*req)
 
-	res, err := deploymentLister.Deployments(functionNamespace).List(sel)
+	res, err := deploymentLister.Deployments(functionNamespace).List(onlyFunctions)
 
 	if err != nil {
 		return nil, err