MAN: Add sssd-systemtap man page
    
    Provide information for administrators and users to utilize
    SSSD systemtap infrastructure.
    
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
    (cherry picked from commit f199c749197532fd3380fa6f5d9f7a579879c21a)