test_upgrade{,_large}: removed use on unportable function

Usage of CORK is not required for upgraded connection,
CORK is not portable. To make test behavior unified for
all supported platforms, CORK usage is removed from tests.

ChangeLog

@@ -1,3 +1,9 @@
+Thu 22 Apr 2021 12:32:00 MSK
+    Fixed some typos.
+    Force disable TCP_CORK, TCP_NOPUSH, and TCP_NODELAY before switching
+    connection to "upgraded" mode.
+    Improved portability of the test-suite for upgraded connections. -EG
+
 Tue 20 Apr 2021 17:11:00 MSK
     Disabled NLS by default in configure. -EG
 

src/microhttpd/test_upgrade.c

@@ -694,8 +694,6 @@ run_usock (void *cls)
 {
   struct MHD_UpgradeResponseHandle *urh = cls;
 
-  MHD_upgrade_action (urh,
-                      MHD_UPGRADE_ACTION_CORK_OFF);
   send_all (usock,
             "Hello");
   recv_all (usock,

src/microhttpd/test_upgrade_large.c

@@ -881,10 +881,6 @@ run_usock (void *cls)
 {
   struct MHD_UpgradeResponseHandle *urh = cls;
 
-  if (MHD_YES !=
-      MHD_upgrade_action (urh,
-                          MHD_UPGRADE_ACTION_CORK_OFF))
-    abort ();
   send_all (usock,
             LARGE_STRING);
   recv_all (usock,