Fix game_ttyrec_datetime to use correct morgue_time.

As it stood Henzell::TtyrecSearch::ttyrecs_for couldn't be used because of this bug in game_ttyrec_datetime but once fixed it works a treat!

I guess all the methods in src/helper.rb want refactoring at some point but I figured it simplest to leave it as is for the time being.

Cheers,
Dan aka broquaint