testing: check_flushing needs to know the host name (#1292)

diff --git a/test/nginx_system_test.sh b/test/nginx_system_test.sh
index 1488bad..4a6a555 100644
--- a/test/nginx_system_test.sh
+++ b/test/nginx_system_test.sh
@@ -1366,7 +1366,7 @@
 
 start_test Follow flushes can be turned off.
 echo "Check that FollowFlushes off outputs a single chunk"
-check_flushing 5.4 1
+check_flushing noflush 5.4 1
 
 start_test Special responses from php are handled OK.
 URL="http://special-response.example.com/A.foo.css.pagespeed.cf.0.css"