REFACTOR: umask(0177) --> umask(SSS_DFL_UMASK)
    
    There are many calls of umask function with 0177 argument. This patch
    add new constant SSS_DFL_UMASK which stands for 0177. So all occurences
    of umask(0177) (except responder code) are replaced by constant
    SSS_DFL_UMASK.
    
    Resolves:
    https://fedorahosted.org/sssd/ticket/2424
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
    (cherry picked from commit c299f997e20011536e365bc18e59e73f68629d2c)