devstack: update package after adding ppa:6wind/virt-mq-ppa repo
devstack: update package after adding ppa:6wind/virt-mq-ppa repo

If package index files is not updated (i.e. apt-get update),
the qemu/libirvit version supporting vhost-user will not be installed.

Change-Id: If64385c56d458109b959ecf2f37f4d8ac41c63d8

stackforge/networking-6wind,openstack/networking-6wind,stackforge/networking-6wind,openstack/networking-6wind