Cleanup handling of config channels in RunSyncLoop

Pass a map of channels instead of a bunch of vars.

My go concurrency-foo is currently weak, so please take a close look:)
This is not safe; you're accessing the map concurrently. You need to send a struct{name string; manifests []api.ContainerManifest} though the updated channel to make it safe. But then you might as well skip this step, give all four watching functions access to the update channel, and have them send that pair through. I can explain in more detail if that's not clear. :)

Thanks for the cleanup-- the current arrangement with four channels has been bugging me.