Remove amqp driver 'unpacked content' logging
Remove amqp driver 'unpacked content' logging

Different OpenStack processes log that line when idle, but it doesn't
offer actionable information to developers or users. Ideally process
logs should be silent when idle, even in debug mode.

Here's a sample:
http://paste.openstack.org/show/201371/

Change-Id: Ib4f63d590a6f5ed295fae12dac12897007b12879

hkumarmk/oslo.messaging,ozamiatin/oslo.messaging,dims/oslo.messaging,magic0704/oslo.messaging,apporc/oslo.messaging,dims/oslo.messaging,dukhlov/oslo.messaging,dukhlov/oslo.messaging,apporc/oslo.messaging,magic0704/oslo.messaging,stevei101/oslo.messaging,zhurongze/oslo.messaging,stevei101/oslo.messaging,isyippee/oslo.messaging,zhurongze/oslo.messaging,hkumarmk/oslo.messaging,isyippee/oslo.messaging,ozamiatin/oslo.messaging