test: de-duplicate test_setup() functions

Now we will run setup_nspawn_root() in some case where do don't need to.

test/TEST-41-ONESHOT-RESTART/test.sh

@@ -3,17 +3,4 @@ set -e
 TEST_DESCRIPTION="Test oneshot unit restart on failure"
 . $TEST_BASE_DIR/test-functions
 
-test_setup() {
-    create_empty_image_rootdir
-
-    (
-        LOG_LEVEL=5
-        eval $(udevadm info --export --query=env --name=${LOOPDEV}p2)
-
-        setup_basic_environment
-        mask_supporting_services
-    )
-    setup_nspawn_root
-}
-
 do_test "$@" 41