[Devstack] Run tempest update in proper time

Recent devstack change [1] changed order of installing things,
where tempest now is installed later than it was. So, run our
tempest updates later too, when tempest is installed.

Closes-Bug: #1646492

[1] I3d98692e69d94756e0034c83a247e05d85177f02

Change-Id: I85ca94455ad0b7882cde70c6ba0091f9f83f39b8

devstack/plugin.sh

@@ -931,11 +931,11 @@ elif [[ "$1" == "stack" && "$2" == "extra" ]]; then
     echo_summary "Creating Manila custom share types"
     create_custom_share_types
 
-    echo_summary "Update Tempest config"
-    update_tempest
-
     echo_summary "Configuring Manila UI"
     configure_manila_ui
+elif [[ "$1" == "stack" && "$2" == "test-config" ]]; then
+    echo_summary "Update Tempest config"
+    update_tempest
 fi
 
 if [[ "$1" == "unstack" ]]; then