Lock import resources on updates to prevent write collisions.

lib/import/base_resource.rb

@@ -91,6 +91,9 @@ module Import
       @resource = lookup_existing(resource, *args)
       return false if !@resource
 
+      # lock the current resource for write access
+      @resource.with_lock do
+
         # delete since we have an update and
         # the record is already created
         resource.delete(:created_by_id)
@@ -117,6 +120,7 @@ module Import
         @resource.save!
         true
       end
+    end
 
     def lookup_existing(resource, *_args)