#76 (3.0.0b3) test.php: $chatter_icon_upload_dir issue

[Alexander Schuch]

The chatter icon upload directory is checked for write
access, even if ALLOW_PRIVATE_IMAGES is set to false.

Suggestion: Check this directory only if
ALLOW_PRIVATE_IMAGES is set to true, so that the
proper box is not red/shown anymore, so that all others
are green and everything looks ok.