modified detection

• 501034tenable_ot_siemens_CVE-2015-1049.nasl • 1.7
• 500840tenable_ot_siemens_CVE-2018-20685.nasl • 1.9
• 500841tenable_ot_siemens_CVE-2019-6109.nasl • 1.9
• 500838tenable_ot_siemens_CVE-2019-6110.nasl • 1.10
• 500898tenable_ot_siemens_CVE-2019-6111.nasl • 1.9
• 501030tenable_ot_siemens_CVE-2021-4034.nasl • 1.12