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/controller/controller.go

@@ -37,7 +37,7 @@ func Start(ctx context.Context, logger *zap.Logger, port int, unitTestFlag bool,
 		cLogger.Fatal("failed to find fission CRDs", zap.Error(err))
 	}
 
-	err = fc.WaitForCRDs()
+	err = crd.WaitForCRDs(fc)
 	if err != nil {
 		cLogger.Fatal("error waiting for CRDs", zap.Error(err))
 	}