Manchester United are into the FA Cup final but there will be few supporters feeling all that positive after such a ridiculous collapse against Coventry City. When United are leading a game 3-0 with 20 minutes to play, the expectation in years gone by has been that the job is done. Yet with this United side, you can never really feel comfortable and Sunday proved exactly why. United threw away a 3-0 lead against Championship side Coventry, going from having one foot in the final to being dragged through extra time. Coventry even had a winning goal ruled out with seconds of extra time to play, …