sdk: Fix ownership of /home/user

After commit a7e7e101 `/home/user` has been owned by `root:root`,
breaking grahical login among the others.

This is because we are no longer creating `/home/user` when creating the
user itself, but `scripts/clone-sample-repos.sh` does
`mkdir -p /home/user/sample-applications/` and then
`chown user:user -R /home/user/sample-applications/`, leaving
`/home/user/` with the wrong owner.

Forcing the creation of the homedir addresses the issue.

Fixes: APERTIS-5527
Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>