Define context.roles with base class
Define context.roles with base class

In f383bd2973c58c5272504603e4f9dddd55c5bb68, oslo.context (2.2.0)
added roles support in the context itself. This passes roles to
super()__init__.

Change-Id: If38d7bb60388e98c8d9c395c2ee127894d70711b

igor-toga/local-snat,eayunstack/neutron,openstack/neutron,noironetworks/neutron,cloudbase/neutron,openstack/neutron,mahak/neutron,huntxu/neutron,huntxu/neutron,sebrandon1/neutron,openstack/neutron,cloudbase/neutron,eayunstack/neutron,noironetworks/neutron,bigswitch/neutron,mahak/neutron,mahak/neutron,igor-toga/local-snat,bigswitch/neutron,sebrandon1/neutron