plugins.inc: $info used on both sides of foreach

Short version: the return value of ctools_plugin_api_include() is busted.
Long version: see patch.

(I'm not sure which naming conventions you prefer for this $info variable and whether you want to change it on one side or on the other, and I don't mind either. If you apply a working fix with whatever variable renaming, that's totally ok for me.)

Please review and commit at your liking.