BUG: Each call to Spinner.update() should just update the spinner once; the value argument should be ignored.
BUG: Each call to Spinner.update() should just update the spinner once;
the value argument should be ignored.

Also delete unnecessary self._obj.__enter__ line in
ProgressBarOrSpinner.__enter__, since it's a no-op for the two types of
objects wrapped by ProgressBarOrSpinner.

pllim/astropy,saimn/astropy,StuartLittlefair/astropy,astropy/astropy,lpsinger/astropy,mhvk/astropy,larrybradley/astropy,lpsinger/astropy,pllim/astropy,mhvk/astropy,aleksandr-bakanov/astropy,astropy/astropy,larrybradley/astropy,larrybradley/astropy,StuartLittlefair/astropy,mhvk/astropy,aleksandr-bakanov/astropy,lpsinger/astropy,saimn/astropy,aleksandr-bakanov/astropy,larrybradley/astropy,mhvk/astropy,aleksandr-bakanov/astropy,astropy/astropy,pllim/astropy,pllim/astropy,lpsinger/astropy,StuartLittlefair/astropy,mhvk/astropy,saimn/astropy,StuartLittlefair/astropy,lpsinger/astropy,larrybradley/astropy,astropy/astropy,pllim/astropy,astropy/astropy,saimn/astropy,saimn/astropy,StuartLittlefair/astropy