Thanks @Tom-Elliott, I have successfully captured and deployed Debian 9 clients both in virtual space and to real hardware. So, it looks like your fix works. I did notice some slower booting as you mentioned but that seemed to be minimized after I went through a full capture-deploy-capture sequence. Perhaps there was residual file system ambiguities that was affecting the boot times. In any event, the boot times smoothed out over time. The only slightly odd thing I did notice is sometimes the client would boot twice before the capture would actually start. I cannot reproduce this all the time. Just thought I would mention it if it makes you think of anything.
Thanks again; will this fix make it into 1.4.5?