Improve test to detect improper header list handling

Author: oxpa

t/020-subrequest.t

@@ -13,6 +13,7 @@ repeat_each(2);
 
 plan tests => repeat_each() * (blocks() * 3 + 23);
 
+$ENV{MALLOC_PERTURB_} = 9;
 $ENV{TEST_NGINX_MEMCACHED_PORT} ||= 11211;
 $ENV{TEST_NGINX_HTML_DIR} ||= html_dir();
 

t/111-req-header-ua.t

@@ -10,6 +10,8 @@ repeat_each(2);
 
 plan tests => repeat_each() * (4 * blocks());
 
+$ENV{MALLOC_PERTURB_} = 9;
+
 #no_diff();
 no_long_string();