Fix extra specs for share type

In case the backends don't have the same capabilities
share creation can fail. For instance, if one of the
backend has the ability to create share from snapshot
and the other does not.
In case "capability_create_share_from_snapshot_support"
parameter is defined in tempest.conf and it is also
specified in extra specs one of the share will fail to
create.

Change-Id: Iade5b2658df59b7d6cdc9f69418afb16a0108353
diff --git a/manila_tempest_tests/tests/api/admin/test_multi_backend.py b/manila_tempest_tests/tests/api/admin/test_multi_backend.py
index 808debe..11feb5e 100644
--- a/manila_tempest_tests/tests/api/admin/test_multi_backend.py
+++ b/manila_tempest_tests/tests/api/admin/test_multi_backend.py
@@ -64,10 +64,10 @@
                 cls.__name__ + "-share-type-%s" % backend)
             extra_specs = {
                 "share_backend_name": backend,
+                "driver_handles_share_servers":
+                    CONF.share.multitenancy_enabled,
             }
-            st = cls.create_share_type(
-                name=st_name,
-                extra_specs=cls.add_extra_specs_to_dict(extra_specs))
+            st = cls.create_share_type(name=st_name, extra_specs=extra_specs)
             cls.sts.append(st["share_type"])
             st_id = st["share_type"]["id"]
             share_data_list.append({"kwargs": {