Agg backend doesn't draw line to arc start point

[corranwebster]

Given:

x, y = 100, 100
gc.begin_path()
gc.move_to(x - 12, y - 12)
gc.arc(x, y, 12.0, 0.0, np.pi)
gc.line_to(x - 12, y - 12)
gc.draw_path()

Compare Agg: vs. Quartz:

From the documentation: https://github.com/enthought/enable/blob/bb2c358248ef72c03d62b2563985f01e1dad6977/kiva/basecore2d.py#L607-L609