util: add is_files_provider() helper
In a bunch of differente places we end up checking whether the domain's
provider is the "files" provider or not.
Let's just add some helper function to standardize the checks.
Signed-off-by: Fabiano FidĂȘncio <fidencio@redhat.com>
Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>