Remove unconditional error log in zipper

[martialblog]

Hi,

while working with carbonapi I noticed a strange error in the logs "DEBUG ERROR LOGGGGG"

Few lines below the removed line there's a debug with with the config, so I just removed the error logggggg.

	logger.Debug("zipper config",
		zap.Any("config", cfg),
	)

I assume this is something that was leftover from debugging something.

Regards
Markus