Make CLI functions return error instead of fatal out (#1379)

Before this PR, CLI functions fatal out when encountering error
instead of returning it. Such behavior makes it hard to reuse 
the functions nor writing unit tests. This PR aims to make functions 
return errors instead of error out.

pkg/fission-cli/cmd/function/test.go

@@ -30,7 +30,6 @@ import (
 
 	"github.com/fission/fission/pkg/controller/client"
 	"github.com/fission/fission/pkg/fission-cli/cliwrapper/cli"
-	"github.com/fission/fission/pkg/fission-cli/cmd"
 	"github.com/fission/fission/pkg/fission-cli/cmd/httptrigger"
 	"github.com/fission/fission/pkg/fission-cli/util"
 )
@@ -40,14 +39,18 @@ type TestSubCommand struct {
 }
 
 func Test(flags cli.Input) error {
+	c, err := util.GetServer(flags)
+	if err != nil {
+		return err
+	}
 	opts := TestSubCommand{
-		client: cmd.GetServer(flags),
+		client: c,
 	}
 	return opts.do(flags)
 }
 
 func (opts *TestSubCommand) do(flags cli.Input) error {
-	m, err := cmd.GetMetadata("name", "fnNamespace", flags)
+	m, err := util.GetMetadata("name", "fnNamespace", flags)
 	if err != nil {
 		return err
 	}
@@ -55,8 +58,10 @@ func (opts *TestSubCommand) do(flags cli.Input) error {
 	routerURL := os.Getenv("FISSION_ROUTER")
 	if len(routerURL) == 0 {
 		// Portforward to the fission router
-		localRouterPort := util.SetupPortForward(util.GetFissionNamespace(),
-			"application=fission-router")
+		localRouterPort, err := util.SetupPortForward(util.GetFissionNamespace(), "application=fission-router")
+		if err != nil {
+			return err
+		}
 		routerURL = "127.0.0.1:" + localRouterPort
 	} else {
 		routerURL = strings.TrimPrefix(routerURL, "http://")
@@ -158,7 +163,12 @@ func printPodLogs(flags cli.Input) error {
 		return errors.New("need --name argument.")
 	}
 
-	queryURL, err := url.Parse(util.GetServerUrl())
+	u, err := util.GetApplicationUrl("application=fission-api")
+	if err != nil {
+		return err
+	}
+
+	queryURL, err := url.Parse(u)
 	if err != nil {
 		return errors.Wrap(err, "error parsing the base URL")
 	}