shutdownHaskellAndExit: just do a normal hs_exit() (#5402)
shutdownHaskellAndExit: just do a normal hs_exit() (#5402)

If we want to keep the RTS alive a bit longer by having another
hs_init()/hs_exit() pair in a library that will destruct itself after
main() has exited, then the forced shutdown here thwarts that.

I think we just "fixed" #5402 in the wrong way before, this should be
better.

sdiehl/ghc,ezyang/ghc,ezyang/ghc,sdiehl/ghc,mettekou/ghc,snoyberg/ghc,mettekou/ghc,olsner/ghc,snoyberg/ghc,sdiehl/ghc,snoyberg/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,snoyberg/ghc,shlevy/ghc,sdiehl/ghc,shlevy/ghc,olsner/ghc,sdiehl/ghc,olsner/ghc,olsner/ghc,mettekou/ghc,shlevy/ghc,snoyberg/ghc,olsner/ghc,shlevy/ghc,snoyberg/ghc,mettekou/ghc,sdiehl/ghc,olsner/ghc,snoyberg/ghc,mettekou/ghc,shlevy/ghc,mettekou/ghc,ezyang/ghc,olsner/ghc,shlevy/ghc,ezyang/ghc,mettekou/ghc,ezyang/ghc,sdiehl/ghc