Don't override images client in compute admin tests

Tests should be explicit about their use of admin credentials. The
base compute admin tests class overrode self.image_client with the
admin version. Stop doing that, and introduce a new
self.admin_image_client client that tests can explicitly use.

Needed-by: https://review.opendev.org/c/openstack/whitebox-tempest-plugin/+/805300
Change-Id: I1a0c84b41b1b77d3a618a8f15448909bd12a0742
diff --git a/tempest/api/compute/admin/test_volume.py b/tempest/api/compute/admin/test_volume.py
index cf8c560..549d4fb 100644
--- a/tempest/api/compute/admin/test_volume.py
+++ b/tempest/api/compute/admin/test_volume.py
@@ -48,8 +48,8 @@
 
         :param return image_id: The UUID of the newly created image.
         """
-        image = self.image_client.show_image(CONF.compute.image_ref)
-        image_data = self.image_client.show_image_file(
+        image = self.admin_image_client.show_image(CONF.compute.image_ref)
+        image_data = self.admin_image_client.show_image_file(
             CONF.compute.image_ref).data
         image_file = io.BytesIO(image_data)
         create_dict = {
@@ -60,11 +60,11 @@
             'visibility': 'public',
         }
         create_dict.update(kwargs)
-        new_image = self.image_client.create_image(**create_dict)
-        self.addCleanup(self.image_client.wait_for_resource_deletion,
+        new_image = self.admin_image_client.create_image(**create_dict)
+        self.addCleanup(self.admin_image_client.wait_for_resource_deletion,
                         new_image['id'])
-        self.addCleanup(self.image_client.delete_image, new_image['id'])
-        self.image_client.store_image_file(new_image['id'], image_file)
+        self.addCleanup(self.admin_image_client.delete_image, new_image['id'])
+        self.admin_image_client.store_image_file(new_image['id'], image_file)
 
         return new_image['id']
 
diff --git a/tempest/api/compute/base.py b/tempest/api/compute/base.py
index 922a14c..a6ff965 100644
--- a/tempest/api/compute/base.py
+++ b/tempest/api/compute/base.py
@@ -658,7 +658,7 @@
             cls.os_admin.availability_zone_client)
         cls.admin_flavors_client = cls.os_admin.flavors_client
         cls.admin_servers_client = cls.os_admin.servers_client
-        cls.image_client = cls.os_admin.image_client_v2
+        cls.admin_image_client = cls.os_admin.image_client_v2
         cls.admin_assisted_volume_snapshots_client = \
             cls.os_admin.assisted_volume_snapshots_client