This option sets enable_v1_api in glance-api.conf, a setting that
was removed by change Ia086230cc8c92f7b7dfd5b001923110d5bc55d4d
in July 2018, so remove the devstack option from lib/glance.
It occurs in two other places:
This option is used in lib/cinder to set an option that was removed
from Cinder by change Ice379db9ae83420bacf9e96e242c7515930eae86 in
Queens, so remove the related code.
When this option is False, it is used in lib/tempest to set
[image-feature-enabled]/api_v1 to False in the tempest config file.
However, the default value of ths setting has been False since
change Iab3a209c744375bf2618afc00a3f7731b62f557e in Sept 2018,
so remove the related code.
Change-Id: I4b18a0a388ed7e7a392fabeac613778e0d23dee7
ee5cf747d8