Fix linux serial number retrieval (#2206)

* Change source of serial number in sysInfo function

The serial number returned by the sysInfo function in info_linux.go has been fixed. Previously, it was incorrectly fetched from the Chassis object. Now it is correctly fetched from the Product object. This aligns better with the expected system info retrieval method.

* Fallback to product.Serial in sys info

In case of the chassis is "Default String" or empty then try to use product.serial

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Co-authored-by: Zoltán Papp <zoltan.pmail@gmail.com>

client/system/info_linux.go

@@ -89,5 +89,9 @@ func _getInfo() string {
 func sysInfo() (serialNumber string, productName string, manufacturer string) {
 	var si sysinfo.SysInfo
 	si.GetSysInfo()
-	return si.Chassis.Serial, si.Product.Name, si.Product.Vendor
+	serial := si.Chassis.Serial
+	if (serial == "Default string" || serial == "") && si.Product.Serial != "" {
+		serial = si.Product.Serial
+	}
+	return serial, si.Product.Name, si.Product.Vendor
 }