fixup 63b9d6e7 , log_sys.write_buf can't run in a loop

The write_lock is released after the first time already.

This leaves the hole in the log_write_and_flush logic, some
flush_lock/write_lock waiters could be hanging, until the
background redo log flush comes.

The possibility of that is relatively tiny though.

storage/innobase/log/log0log.cc

@@ -705,12 +705,8 @@ ATTRIBUTE_COLD void log_write_and_flush()
   ut_ad(!srv_read_only_mode);
   if (!log_sys.is_pmem())
   {
-    while (log_sys.write_buf<false>())
-    {
-    }
-    while (log_flush(write_lock.value()))
-    {
-    }
+    log_sys.write_buf<false>();
+    log_flush(write_lock.value());
   }
 #ifdef HAVE_PMEM
   else