if a node is enabled for signups, and you uncheck the box, it's still signup-enabled

this isn't exactly duplicate with either http://drupal.org/node/49007 or http://drupal.org/node/48122, so i'm filing it as a separate issue...

if a node has been enabled for signups (by whatever means you want, we can argue about that later), and someone with the appropriate permissions is editing the node, they're presented with an "Enable signups for this node" checkbox under the "Signup settings" fieldset (care of http://drupal.org/node/67487). for signup-enabled nodes, this checkbox will be checked. however, if you uncheck the box and submit your change, the node continues to be signup enabled. :(

we need something like a a confirm-able button/link to "disable signups" once a node has been signup enabled instead of this checkbox. or, we need to check in the update hook if the box is unchecked, and if so, disable signups. it'd be nicer to use some kind of confirm-able thing, however, since this is a fairly drastic move (especially if there have already been signups for the node), and we should force users to confirm they want to do it.