Removed unused attributes from README
Removed unused attributes from README

These attributes are specified in openstack-common.
Don't see why we should document them inside the wrapper,
should only document attributes the wrapper is setting

Change-Id: Ic4be7505348e0a2d52442f64bcf388f2244e11e6

hubspotdevops/cookbook-openstack-ops-messaging,mattray/cookbook-openstack-ops-messaging,mancdaz/cookbook-openstack-ops-messaging