cri,nri: block NRI plugin sync. during event processing.

Block the synchronization of registering NRI plugins during
CRI events to avoid the plugin ending up in an inconsistent
starting state after initial sync (missing pods, containers
or missed events for some pods or containers).

Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>

internal/nri/nri.go

@@ -81,6 +81,9 @@ type API interface {
 
 	// RemoveContainer relays container removal events to NRI.
 	RemoveContainer(context.Context, PodSandbox, Container) error
+
+	// BlockPluginSync blocks plugin synchronization until it is Unblock()ed.
+	BlockPluginSync() *PluginSyncBlock
 }
 
 type State int
@@ -435,6 +438,15 @@ func (l *local) RemoveContainer(ctx context.Context, pod PodSandbox, ctr Contain
 	return err
 }
 
+type PluginSyncBlock = nri.PluginSyncBlock
+
+func (l *local) BlockPluginSync() *PluginSyncBlock {
+	if !l.IsEnabled() {
+		return nil
+	}
+	return l.nri.BlockPluginSync()
+}
+
 func (l *local) syncPlugin(ctx context.Context, syncFn nri.SyncCB) error {
 	l.Lock()
 	defer l.Unlock()