Glance v1 APIs are deprecated and v2 APIs are current one,
but CONF.image_feature_enabled.api_v1 now defaults to True,
so CONF.image_feature_enabled.api_v1 must be explicitly set
to False in tempest.conf to avoid using api_v1, which is
annoying. So this is to set CONF.image_feature_enabled.api_v1
default to False.
Change-Id: Iab3a209c744375bf2618afc00a3f7731b62f557e