Float comparison issues with time and quantity #6970

>>> import astropy
>>> print(astropy.__version__)
>>> from astropy.time import Time
>>> import astropy.units as u
>>> start = Time('2016-02-06 03:00:00')
>>> duration = 2*u.hour
>>> end_time = start + duration
>>> end_time - duration == start
2.0.2
True

>>> import astropy
>>> print(astropy.__version__)
>>> from astropy.time import Time
>>> import astropy.units as u
>>> start = Time('2016-02-06 03:00:00')
>>> duration = 2*u.hour
>>> end_time = start + duration
>>> print(end_time - duration == start)
>>> print(end_time - duration)
>>> print(start)
3.0.dev20874
False
2016-02-06 03:00:00.000
2016-02-06 03:00:00.000