Add missing docs for list_opts()
Add missing docs for list_opts()

Seems I forgot to check this in as part of commit 0eb5a6f.

Change-Id: I4e3128f726873998fb9c1cde78864e06e225e5bd

apporc/oslo.messaging,ozamiatin/oslo.messaging,eayunstack/oslo.messaging,hkumarmk/oslo.messaging,hkumarmk/oslo.messaging,isyippee/oslo.messaging,magic0704/oslo.messaging,apporc/oslo.messaging,redhat-openstack/oslo.messaging,stevei101/oslo.messaging,redhat-openstack/oslo.messaging,isyippee/oslo.messaging,viggates/oslo.messaging,dims/oslo.messaging,dukhlov/oslo.messaging,magic0704/oslo.messaging,zhurongze/oslo.messaging,zhurongze/oslo.messaging,dukhlov/oslo.messaging,stevei101/oslo.messaging,dims/oslo.messaging,ozamiatin/oslo.messaging