do_sysfile_cmd colon-separates the module path, and then we can't parse it
I'm a bit tentative about this, because it seems such an exceptionally silly and longstanding bug.
The kernel module path is a space separated string. However, 'moddir' in /etc/system creates a colon-separated path. Which we'll then, it seems, treat as a single, always invalid, entry. That seems to mean that any /etc/system file with a 'moddir' entry creates a brick.