NSS: Replace spaces with specified string in names.
    
    This patch add possibility to replace whitespace in user and group names with
    a specified string. With string "-", sssd will return the same result as
    winbind enabled option "winbind normalize names"
    
    Resolves:
    https://fedorahosted.org/sssd/ticket/1854
    
    Reviewed-by: Pavel Reichl <preichl@redhat.com>
    Reviewed-by: Michal Židek <mzidek@redhat.com>
    (cherry picked from commit 21bc143c2855638242e9dfe01ea66198b5883b8a)