Use Clientset interface instead of type for Fission/kubernetes clients (#2416)

Using interface makes it easy to create a fake client and unit test
a specific portion of the code. We should be able to more write unit
test and increase coverage of code with this change.

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>

pkg/timer/main.go

@@ -32,7 +32,7 @@ func Start(ctx context.Context, logger *zap.Logger, routerUrl string) error {
 		return errors.Wrap(err, "failed to get fission or kubernetes client")
 	}
 
-	err = fissionClient.WaitForCRDs()
+	err = crd.WaitForCRDs(fissionClient)
 	if err != nil {
 		return errors.Wrap(err, "error waiting for CRDs")
 	}

pkg/timer/timerSync.go

@@ -23,19 +23,19 @@ import (
 	"go.uber.org/zap"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 
-	"github.com/fission/fission/pkg/crd"
+	"github.com/fission/fission/pkg/generated/clientset/versioned"
 	"github.com/fission/fission/pkg/utils"
 )
 
 type (
 	TimerSync struct {
 		logger        *zap.Logger
-		fissionClient *crd.FissionClient
+		fissionClient versioned.Interface
 		timer         *Timer
 	}
 )
 
-func MakeTimerSync(ctx context.Context, logger *zap.Logger, fissionClient *crd.FissionClient, timer *Timer) *TimerSync {
+func MakeTimerSync(ctx context.Context, logger *zap.Logger, fissionClient versioned.Interface, timer *Timer) *TimerSync {
 	ws := &TimerSync{
 		logger:        logger.Named("timer_sync"),
 		fissionClient: fissionClient,