node options behaviour on editing by non-admin user

Here's the use case:

1. A non-admin user creates a node, the options ('status', 'promote', 'sticky', 'revision') are all set to their node_options defaults. In this case, status is set to published (1), and promote is off (0).

2. The site administrator likes the posting and promotes it to the front page (promote is now 1).

3. The original poster decides to update the node - as per the current node code, it disappears off the front page because the node_options are reset to the defaults.

I would propose that this behaviour is not actually desirable - instead, those node_options should be kept to whatever the site administrator set them to. I can see paranoid cases where the admin might want to review the content before resetting the promote flag, but I think most folks would expect the options to stay the same.

I have attached a small patch to accomplish the proposed change.