Drop use of deprecated collections classes
Drop use of deprecated collections classes

These were moved in Python 3.3 and the aliases will be dropped in 3.10.

Change-Id: I5b289c21f752e3135af86c4180feead8b997f61d
Signed-off-by: Stephen Finucane <4725dc7f3632bf126d9fbdc30c347e91e8d2fe16@redhat.com>

openstack/oslo.context