MDEV-9366 : do_shutdown_server fails to detect server shutdown on Windows.

Fix test whether process is alive in mysqltest.

Also fix SHUT_RD definition on Windows to be SD_RECEIVE.
SD_BOTH  was used instead prior to this patch, and this would
occasionally make mysql_shutdown()  fail - when the socket for the current connection
is not able send the COM_SHUTDOWN response anymore.

client/mysqltest.cc

@@ -5121,12 +5121,13 @@ static int my_kill(int pid, int sig)
 {
 #ifdef __WIN__
   HANDLE proc;
-  if ((proc= OpenProcess(PROCESS_TERMINATE, FALSE, pid)) == NULL)
+  if ((proc= OpenProcess(SYNCHRONIZE|PROCESS_TERMINATE, FALSE, pid)) == NULL)
     return -1;
   if (sig == 0)
   {
+    DWORD wait_result= WaitForSingleObject(proc, 0);
     CloseHandle(proc);
-    return 0;
+    return wait_result == WAIT_OBJECT_0?-1:0;
   }
   (void)TerminateProcess(proc, 201);
   CloseHandle(proc);

include/violite.h

@@ -208,7 +208,7 @@ void vio_end(void);
 
 /* shutdown(2) flags */
 #ifndef SHUT_RD
-#define SHUT_RD SD_BOTH
+#define SHUT_RD SD_RECEIVE
 #endif
 
 /*