[FIX] data dir when home is not a directory

Use site data dir instead of user data dir when user's home is not a directory.
Like system users created with /dev/null as home.

Stricter than before.
Merge pull request #1343 from vice/master

[FIX] data dir when home is not a directory
Merge branch 'master' of https://github.com/odoo/odoo into master-win32