Marking the login_url option as "deprecated_for_removal"

https://review.openstack.org/#/c/212239 has been successfully
merged and now we don't need the login_url option because only
the dashboard_url option is used in the dashboard test. This patch
is intended to mark CONF.dashboard.login_url as deprecated_for_removal.

Change-Id: I4195478d93da605218fddf9aa896e2804ab442ac
1 file changed