Remove TEMPEST_ENABLE_NOVA_XML_API from Tempest config

I5b3e221d942e09134024b82acaf179dc869357e0 has removed xml_api_v2 from
Tempest config, and xml_api_v2 setting of DevStack is unnecessary now.
This patch removes it.

Change-Id: Ic85fbfda13fd352c4d513859915aaca27e894b58
diff --git a/lib/tempest b/lib/tempest
index 6bcfaec..46c9e26 100644
--- a/lib/tempest
+++ b/lib/tempest
@@ -304,7 +304,6 @@
     iniset $TEMPEST_CONFIG compute-feature-enabled change_password False
     iniset $TEMPEST_CONFIG compute-feature-enabled block_migration_for_live_migration ${USE_BLOCK_MIGRATION_FOR_LIVE_MIGRATION:-False}
     iniset $TEMPEST_CONFIG compute-feature-enabled api_extensions ${COMPUTE_API_EXTENSIONS:-"all"}
-    iniset $TEMPEST_CONFIG compute-feature-enabled xml_api_v2 ${TEMPEST_ENABLE_NOVA_XML_API:-True}
     iniset $TEMPEST_CONFIG compute-feature-disabled api_extensions ${DISABLE_COMPUTE_API_EXTENSIONS}
 
     # Compute admin