Comment 7 for bug 1718966

I've made a small change creating a unit file slightly different from the one already present in systemd-204, considering different dependencies for this usage (mounting/umounting volumes when upstart has already taken part on it).

The result is here: http://pastebin.ubuntu.com/25663762/

As you can see, after installing the new packages, being proposed in this fix, snapd can work again mounting all new squash filesystems it depends on.

- Attaching the debdiff for SRU.
- Requesting SRU sponsoring.
- Will verify once it gets uploaded to -proposed.