Remove explicit oslo.messaging version requirement
Remove explicit oslo.messaging version requirement

This will help us support both the current (kilo) trunk and previous
releases.

Change-Id: I4f6d814df50668fb3009ef5fa5c271f02dc51b8c

muraliselva10/cloudkitty,FNST-OpenStack/cloudkitty,stackforge/cloudkitty,FNST-OpenStack/cloudkitty,muraliselva10/cloudkitty,openstack/cloudkitty,stackforge/cloudkitty,openstack/cloudkitty