sysdb: sanitize search filter input
    
    This patch sanitizes the input for sysdb searches by UPN/email, SID and
    UUID.
    
    This security issue was assigned CVE-2017-12173
    
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
    Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>