appengine/aetest: prevent dev_appserver from monitoring file changes during test

Fixes #12456.

Change-Id: Id918c73a1f27f26ab11f2a6363385e6eff393552
diff --git a/aetest/instance_vm.go b/aetest/instance_vm.go
index 0281d3f..271d9e6 100644
--- a/aetest/instance_vm.go
+++ b/aetest/instance_vm.go
@@ -185,6 +185,7 @@
 		"--port=0",
 		"--api_port=0",
 		"--admin_port=0",
+		"--automatic_restart=false",
 		"--skip_sdk_update_check=true",
 		"--clear_datastore=true",
 		"--clear_search_indexes=true",