Allow setting the SNMP version for check_iftraffic.pl

This is not supported in check_iftraffic.pl master yet
but there's a pull request at https://github.com/NETWAYS/check_iftraffic/pull/4

itl/plugins-contrib.d/network-components.conf

@@ -297,6 +297,10 @@ object CheckCommand "iftraffic" {
 			value = "$iftraffic_community$"
 			description = "SNMP community. Defaults to 'public' if omitted."
 		}
+		"-V" = {
+			value = "$iftraffic_version$"
+			description = "SNMP version. Defaults to '1' if omitted."
+		}
 		"-i" = {
 			value = "$iftraffic_interface$"
 			description = "Interface name."