buf_page_get_low(): If the page was read-fixed, validate the page ID
because the page could have been marked as corrupted. We should retry
the page read in this case, instead of returning a soon-to-be-evicted
corrupted page to the caller.

This was initially only observed on Microsoft Windows.
On Linux, this was repeated after adding a sleep
to buf_pool_t::corrupted_evict() between
bpage->zip.fix.fetch_sub() and bpage->lock.x_unlock().