Remove btif enable state management

It's no longer necessary with the stack manager.

With these changes I don't think we'll be able to handle clean_up
as a result of an enable timeout coming down from Java.
But I think I'm ok with that.

At that point we're already hosed because of something else
which should be fixed. And if we wanted to handle clean_up during
start_up we'd violate the mutually exclusive guarantees the stack
management thread makes about init/start_up/shut_down/clean_up.
3 files changed