Title: #703: nss: sssd returns '/' for emtpy home directories
This should probably not be specific to the files provider.
An empty home directory is a valid value and should be returned as is if the source
database specifies an empty string.
That's true but files provider is quite different from the others. Other
providers have homedir fallback templates and other features around homedir. So we (I)
want to deal with them separately. Probably in next PR
See the full comment at https://github.com/SSSD/sssd/pull/703#issuecomment-443766083