node_load on mail_alter hook might be getting an old node from the cache

I found out that when a simplenews node was edited and a test newsletter was requested to be sent in the same moment, the unmodified simplenews node was sent as a test instead of the new one.

I debugged this issue and I found it's related to #221081: Entity cache out of sync and inconsistent when saving/deleting entities.

Rather than patching the core, there's a workaround you can use on this module, which is to fix the node_load() funtion to use both nid and vid in the mail_alter hook.