Update default container registry to quay.io
Update default container registry to quay.io

The constant for tripleoclient was still set to docker.io instead of
quay.io.

Change-Id: I2450e0fe2f497c9e627a1e75924a447b10c2b570
Signed-off-by: James Slagle <33ab48cedd1a7cf7a68e1b587db88f55f753652f@redhat.com>

openstack/python-tripleoclient