Some filter generators will not write to STDOUT

[emcconville]

# cif CIStripesGenerator -size 100x100 STDOUT | identify -
Unable to write to file:///dev/stdout
-=>/var/tmp/magick-53966YSpwnUg35OPw PNG 100x100 100x100+0+0 8-bit sRGB 1.54KB 0.000u 0:00.000

[emcconville]

Looks like "STDOUT" is not auto-closing when checking if write-to operation was successful. This is normal behavior, so adjusting success write logic to handle STDOUT writing.