Remove isInteractive hack
Remove isInteractive hack

This commit removes the 'isInteractive' function in favour of simpler
logic, where we call 'parseModule' with a "cleaned" DynFlags (without
the plugins) to avoid any recursive call.

ucsd-progsys/liquidhaskell,ucsd-progsys/liquidhaskell,ucsd-progsys/liquidhaskell,ucsd-progsys/liquidhaskell,ucsd-progsys/liquidhaskell,ucsd-progsys/liquidhaskell