Probe (open and close) the CI Drive before calling blkid

This fixes a strange bug where the first call to /dev/fd0
fails with an IO error. Probably due to the O_NONBLOCK flag
added here:
https://git.kernel.org/pub/scm/utils/util-linux/util-linux.git/commit/libblkid/src/verify.c?id=39f5af25982d8b0244000e92a9d0e0e6557d0e17

pkg/cloudinit/cloudinit.go

@@ -92,7 +92,14 @@ func ReadData() (*Data, error) {
 }
 
 func GetDeviceAttr(device, attr string) (string, error) {
-	out, err := exec.Command("blkid", "-ovalue", "-t", "TYPE=iso9660", "-s", strings.ToUpper(attr), device).CombinedOutput()
+	// Check device availability
+	if fd, err := os.Open(device); err == nil {
+		fd.Close()
+	} else {
+		return "", err
+	}
+
+	out, err := exec.Command("blkid", "-c", "/dev/null", "-ovalue", "-t", "TYPE=iso9660", "-s", strings.ToUpper(attr), device).CombinedOutput()
 	if err != nil {
 		var exitCode int
 		if exiterr, ok := err.(*exec.ExitError); ok {