I tried to follow along as I am having similar problems with mounts in Docker Beta windows. I got a different error after the final mount:
mount error(13): Permission denied
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)
This was with a new user and a simple alpha-only password, and a restart, unshare, reshare. Trying to browse the c-drive gives me ‘Windows can’t find ‘\10.0.0.75.1\c’. Check the spelling and try again.’