Fix a comment.
Fix some whitespace.
Panic if we find a block on the wrong list, that's not something we can
recover from.
Fix comment.
whitespace
If a page is reconciled (causing it's on-disk blocks to be free'd and
potentially recycled), and then a subsequent collapse of a stack of
split-merge pages replaces that page with a page that has not yet been
reconciled, we can potentially free the same blocks twice.  The fix is
to clear the page's WT_REF.addr field at the time we free the blocks,
so future reconciliations will ignore the original disk blocks.

Explicitly free the disk blocks instead of copying them into the
reconciliation tracking array and then freeing them, that gets rid of
the __wt_rec_track_onpage_ref() function, will be faster for a common
operation, and isn't logically different, the next step is to free the
blocks anyway.