files: do not apply override_shell to files provider
override_shell should not be applied to files provider as the provider
should always return *only* what's in the files and nothing else.
Resolves:
https://pagure.io/SSSD/sssd/issue/3758
Signed-off-by: Fabiano FidĂȘncio <fidencio@redhat.com>
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>