I tried various arrangements for the call to __wt_split_page_inmem, but ended up adding the code here. The trouble is that it's unique in that we want to call ```__rec_page_dirty_update```, but we don't want to call ```__rec_discard_tree```.

I did try having the call to __wt_split_page_inmem inlined in __rec_review, and having that code call dirty update then returning EBUSY. The trouble is that then __rec_evict calls __rec_excl_clear which hits an assertion.

In the end the try_split return parameter was the least invasive change I could find.