modified detection

• 500871tenable_ot_schneider_CVE-2017-6028.nasl • 1.10
• 500862tenable_ot_schneider_CVE-2017-6026.nasl • 1.9
• 500867tenable_ot_schneider_CVE-2017-6030.nasl • 1.9
• 501682tenable_ot_siemens_CVE-2017-12734.nasl • 1.6
• 501675tenable_ot_siemens_CVE-2017-12735.nasl • 1.6
• 500107tenable_ot_siemens_CVE-2017-9946.nasl • 1.11
• 500105tenable_ot_siemens_CVE-2017-9947.nasl • 1.11