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

In Ia575ba803a0fb70f39146bd75d381ed19414bd23, oslo.context (2.2.0)
added roles support in the context itself. This passes roles to
super()__init__ and uses the default to_dict().

Depends-On: I79ea029ceb67173e69631b4e6e614fa62e159227
Change-Id: I1807f19aa867f17c055bb018b6cce6f569f90ca4

DavidPurcell/murano_temp,openstack/murano,openstack/murano,DavidPurcell/murano_temp,DavidPurcell/murano_temp,DavidPurcell/murano_temp