After a couple poor weekends out of the gate, ‘John Carter’ is poised to become one of the worst movie investments in history. Analysts expect the Walt Disney Co. to take a $165 million loss that will earn it the indignity cast upon forgettable films like ‘Ishtar’ and ‘Howard the Duck.’ A variety of reasons for the movie’s poor performance have been floated — from casting to plot to promotion. Wha