Clean _header before copying
Clean _header before copying

This removes the need to clean it up in name setting. Previously
I had thought that _header should not be touched automatically
unless requested.

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