innodb_log_file_size_update(): Wait for buf_pool.done_flush_list
(that a flush batch has completed), not buf_pool.do_flush_list
(that the buf_flush_page_cleaner was woken up).

The condition variable buf_pool.done_flush_list is broadcast by the
buf_flush_page_cleaner() at the end of each batch, which is when the
log checkpoint can advance and where any log resizing may be completed.
The purpose of the condition variable buf_pool.do_flush_list is to
wake up the buf_flush_page_cleaner() thread because there is work to do.
If no thread is signaling that condition variable, this loop could
unnecessarily wait for up to 5 seconds too long for the log resizing
to be completed. By consuming signals it could also prevent the
buf_flush_page_cleaner() thread from waking up.

Tested by: Matthias Leich