Tests: adjusted limit_req rate value.

This shortens excessive test execution time due to unnecessarily delayed
backend connection after client connection close, which is usually observed
when the client connection is closed before the request is proxied to backend.

limit_conn.t

diff --git a/limit_conn.t b/limit_conn.t
index 5816224..d5dd2e2 100644
--- a/limit_conn.t
+++ b/limit_conn.t
@@ -39,7 +39,7 @@
 http {
     %%TEST_GLOBALS_HTTP%%
 
-    limit_req_zone   $binary_remote_addr  zone=req:1m rate=1r/m;
+    limit_req_zone   $binary_remote_addr  zone=req:1m rate=30r/m;
 
     limit_conn_zone  $binary_remote_addr  zone=zone:1m;
     limit_conn_zone  $binary_remote_addr  zone=zone2:1m;