Enable admin_domain_scope by default in Tempest

Tempest introduced a new ability to use domain scoped tokens for
identity v3 admin APIs. Since domain scoped tokens can be used
with the base keystone policy used in the gate, and the
pre-provisioned admin user is assigned a role on the domain, turn
the option alway on.

Change-Id: Ib1bb958eee076364b407fc03e77e6882d92147d2
Depends-on: I91ca907992428a5a14fb8d48a4fad105d2906e27
diff --git a/lib/tempest b/lib/tempest
index 3cd300c..4ddff57 100644
--- a/lib/tempest
+++ b/lib/tempest
@@ -261,6 +261,8 @@
     # Identity
     iniset $TEMPEST_CONFIG identity uri "$KEYSTONE_SERVICE_PROTOCOL://$KEYSTONE_SERVICE_HOST:5000/v2.0/"
     iniset $TEMPEST_CONFIG identity uri_v3 "$KEYSTONE_SERVICE_URI_V3"
+    # Use domain scoped tokens for admin v3 tests, v3 dynamic credentials of v3 account generation
+    iniset $TEMPEST_CONFIG identity admin_domain_scope True
     if [[ "$TEMPEST_HAS_ADMIN" == "True" ]]; then
         iniset $TEMPEST_CONFIG auth admin_username $admin_username
         iniset $TEMPEST_CONFIG auth admin_password "$password"