Tests: testing worker_shutdown_timeout works with HTTP/2.

A request in HTTP/2 is ensured to be finalized with worker_shutdown_timeout
by testing that it is logged at least, and the status code is not set as it
would on proxy_read_timeout.  After the fix has been fixed in ab5cac9d3f00,
the latter can be tuned to a safer value without losing in execution time.

worker_shutdown_timeout_h2.t

diff --git a/worker_shutdown_timeout_h2.t b/worker_shutdown_timeout_h2.t
index fcde6ce..f487c1d 100644
--- a/worker_shutdown_timeout_h2.t
+++ b/worker_shutdown_timeout_h2.t
@@ -23,7 +23,7 @@
 select STDERR; $| = 1;
 select STDOUT; $| = 1;
 
-my $t = Test::Nginx->new()->has(qw/http http_v2 proxy/)->plan(1);
+my $t = Test::Nginx->new()->has(qw/http http_v2 proxy/)->plan(2);
 
 $t->write_file_expand('nginx.conf', <<'EOF');
 
@@ -44,7 +44,7 @@
 
         location / {
             proxy_pass http://127.0.0.1:8081;
-            proxy_read_timeout 200ms;
+            proxy_read_timeout 5s;
         }
     }
 }
@@ -61,6 +61,13 @@
 select undef, undef, undef, 0.1;
 $t->stop();
 
+TODO: {
+local $TODO = 'not yet' unless $t->has_version('1.17.4');
+
+like($t->read_file('access.log'), qr/ (?!504)\d{3} /, 'shutdown timeout');
+
+}
+
 $t->todo_alerts() unless $t->has_version('1.17.4');
 
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