nova: remove allow_migrate_to_same_host config usage

Nova commit 9b224641295af3763d011816d6399565ac7b98de removed the option
in Liberty so we can remove it's usage in devstack.

Related-Bug: #1364851

Change-Id: If051f43fb75d57c118db4e8e97895ff06fbb54e2
diff --git a/lib/nova b/lib/nova
index 807dfce..75e585d 100644
--- a/lib/nova
+++ b/lib/nova
@@ -392,7 +392,6 @@
     iniset $NOVA_CONF DEFAULT debug "$ENABLE_DEBUG_LOG_LEVEL"
     if [ "$NOVA_ALLOW_MOVE_TO_SAME_HOST" == "True" ]; then
         iniset $NOVA_CONF DEFAULT allow_resize_to_same_host "True"
-        iniset $NOVA_CONF DEFAULT allow_migrate_to_same_host "True"
     fi
     iniset $NOVA_CONF DEFAULT api_paste_config "$NOVA_API_PASTE_INI"
     iniset $NOVA_CONF DEFAULT rootwrap_config "$NOVA_CONF_DIR/rootwrap.conf"