suppressed a valgrind false positive in libdl.

Author: agentzh

valgrind.suppress

@@ -318,4 +318,14 @@ fun:main
    fun:ngx_init_cycle
    fun:main
 }
-
+{
+   <insert_a_suppression_name_here>
+   Memcheck:Cond
+   fun:index
+   fun:expand_dynamic_string_token
+   fun:_dl_map_object
+   fun:map_doit
+   fun:_dl_catch_error
+   fun:do_preload
+   fun:dl_main
+}