Fix race in API related to LoadComplete()

LoadComplete() modifies object, so it would cause issues if it runs
concurrently with other methods. Uprage mutex locks to write
locks when LoadComplete() is being used.

api/graph.go

@@ -24,14 +24,14 @@ func apiGraph(c *gin.Context) {
 
 	factory := context.CollectionFactory()
 
-	factory.RemoteRepoCollection().RLock()
-	defer factory.RemoteRepoCollection().RUnlock()
-	factory.LocalRepoCollection().RLock()
-	defer factory.LocalRepoCollection().RUnlock()
-	factory.SnapshotCollection().RLock()
-	defer factory.SnapshotCollection().RUnlock()
-	factory.PublishedRepoCollection().RLock()
-	defer factory.PublishedRepoCollection().RUnlock()
+	factory.RemoteRepoCollection().Lock()
+	defer factory.RemoteRepoCollection().Unlock()
+	factory.LocalRepoCollection().Lock()
+	defer factory.LocalRepoCollection().Unlock()
+	factory.SnapshotCollection().Lock()
+	defer factory.SnapshotCollection().Unlock()
+	factory.PublishedRepoCollection().Lock()
+	defer factory.PublishedRepoCollection().Unlock()
 
 	graph, err := deb.BuildGraph(factory, layout)
 	if err != nil {