Tests: HTTP/2 tests speedup.

Similar to a78eedc39484, this change disables lingering_close in those tests
that depend on open connections during graceful shutdown for testing alerts.
It was ensured that disabling lingering_close does not cover alerts on older
versions.

h2_ssl.t

diff --git a/h2_ssl.t b/h2_ssl.t
index 907fb31..a4b2a2b 100644
--- a/h2_ssl.t
+++ b/h2_ssl.t
@@ -48,6 +48,8 @@
         ssl_certificate_key localhost.key;
         ssl_certificate localhost.crt;
 
+        lingering_close off;
+
         location / { }
     }
 }

h2_ssl_proxy_cache.t

diff --git a/h2_ssl_proxy_cache.t b/h2_ssl_proxy_cache.t
index 74dcfb2..9cc70b8 100644
--- a/h2_ssl_proxy_cache.t
+++ b/h2_ssl_proxy_cache.t
@@ -51,6 +51,7 @@
         ssl_certificate localhost.crt;
 
         send_timeout 1s;
+        lingering_close off;
 
         location / {
             proxy_pass   http://127.0.0.1:8081;