r3727: Update from Rob Foehl (rwf@loonybin.net):

r3727: Update from Rob Foehl (rwf@loonybin.net):
Try modifying printer before adding it,since add logic appends ObjectClass to mods, which caused a contraint violation when modifying an already published printer.

Also cleanup the check_published_printers() logic when verifying published status on startup.
(This used to be commit 82eb168c827b4b7310b42c0f36c504e0fa16dc99)