Work around AOL Server SIGCHLD issue.

Image resizing spawns a child process (ImageMagick convert) and when that child completes, it raises a SIGCHLD to let the parent process know it is one.  AOL Server does not handle this signal, and the ACS thinks the image resize failed.

Add a wrapper prodedure that treats this SIGCHLD "error" as a success and use it when we resize images.