Add controller API client interface (#1467)

This PR adds an interface for controller API client, it allows us to
implement mock API client for unit testing with ease and we are
able to generate spec file without accessing the real Fission server.

pkg/fission-cli/cmd/spec/init.go

@@ -26,27 +26,20 @@ import (
 	"github.com/pkg/errors"
 	uuid "github.com/satori/go.uuid"
 
-	"github.com/fission/fission/pkg/controller/client"
 	"github.com/fission/fission/pkg/fission-cli/cliwrapper/cli"
+	"github.com/fission/fission/pkg/fission-cli/cmd"
 	spectypes "github.com/fission/fission/pkg/fission-cli/cmd/spec/types"
 	flagkey "github.com/fission/fission/pkg/fission-cli/flag/key"
 	"github.com/fission/fission/pkg/fission-cli/util"
 )
 
 type InitSubCommand struct {
-	client       *client.Client
+	cmd.CommandActioner
 	deployConfig *spectypes.DeploymentConfig
 }
 
 func Init(input cli.Input) error {
-	c, err := util.GetServer(input)
-	if err != nil {
-		return err
-	}
-	opts := InitSubCommand{
-		client: c,
-	}
-	return opts.do(input)
+	return (&InitSubCommand{}).do(input)
 }
 
 func (opts *InitSubCommand) do(input cli.Input) error {