Separate Image v1 members client

Separate image v1 members APIs method into new
member client from Image client.

Partially implements blueprint consistent-service-method-names

Change-Id: If52092f39e05701d4c19809bbaa1c234c2ce8e08
diff --git a/tempest/api/image/base.py b/tempest/api/image/base.py
index bd04c0d..377cc98 100644
--- a/tempest/api/image/base.py
+++ b/tempest/api/image/base.py
@@ -93,12 +93,14 @@
     @classmethod
     def setup_clients(cls):
         super(BaseV1ImageMembersTest, cls).setup_clients()
+        cls.image_member_client = cls.os.image_member_client
+        cls.alt_image_member_client = cls.os_alt.image_member_client
         cls.alt_img_cli = cls.os_alt.image_client
 
     @classmethod
     def resource_setup(cls):
         super(BaseV1ImageMembersTest, cls).resource_setup()
-        cls.alt_tenant_id = cls.alt_img_cli.tenant_id
+        cls.alt_tenant_id = cls.alt_image_member_client.tenant_id
 
     def _create_image(self):
         image_file = moves.cStringIO(data_utils.random_bytes())