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/buildwatch.go

@@ -34,7 +34,7 @@ type (
 	// packageBuildWatcher is used to watch a set of in-progress builds.
 	packageBuildWatcher struct {
 		// fission client
-		fclient *client.Client
+		fclient client.Interface
 
 		// set of packages already printed, ensures we don't duplicate the notifications
 		finished map[string]bool
@@ -44,7 +44,7 @@ type (
 	}
 )
 
-func makePackageBuildWatcher(fclient *client.Client) *packageBuildWatcher {
+func makePackageBuildWatcher(fclient client.Interface) *packageBuildWatcher {
 	return &packageBuildWatcher{
 		fclient:  fclient,
 		finished: make(map[string]bool),
@@ -68,7 +68,7 @@ func (w *packageBuildWatcher) watch(ctx context.Context) {
 		}
 
 		// pull list of packages (TODO: convert to watch)
-		pkgs, err := w.fclient.PackageList(metav1.NamespaceAll)
+		pkgs, err := w.fclient.V1().Package().List(metav1.NamespaceAll)
 		if err != nil {
 			fmt.Printf("Getting list of packages: %v", err)
 			os.Exit(1)