tests: suppressed a valgrind false positive in the latest nginx core.

Author: agentzh

valgrind.suppress

@@ -223,3 +223,12 @@ fun:ngx_http_lua_handle_subreq_responses
  fun:do_preload
  fun:dl_main
 }
+{
+ <insert_a_suppression_name_here>
+ Memcheck:Leak
+ match-leak-kinds: definite
+ fun:malloc
+ fun:ngx_alloc
+ fun:ngx_set_environment
+ fun:ngx_single_process_cycle
+}