cache_req: no refresh with CACHE_REQ_BYPASS_PROVIDER
    
    This patch fixes an unexpected behavior of the cache request code if the
    CACHE_REQ_BYPASS_PROVIDER option is used. Currently even if this option
    is used an expired entry in the cache is refreshed by calling the
    provider. With this patch an error is returned if the entry is expired
    and the provider is not called.
    
    Resolves: https://pagure.io/SSSD/sssd/issue/4098
    
    Reviewed-by: Pavel Březina <pbrezina@redhat.com>