Clean dead code from entrynodes.c

I see dead code in entrynodes.c.

There are three blocks of #if 0 code. One of them is particularly annoying because it's in the middle of choose_random_entry_impl() which is an important function, and it makes it harder to read.

I would say that all dead code needs to go to the graveyard (git history in our case).

(We might want to keep the dead code in control_event_guard_deferred(), which is currently a NOP, just to show what that function used to be.)