Fix dracut failure when loading system fs.

[javiercplus]

dracut-ng/dracut@bbd2613
chore(dmsquash-live): remove support for ext3fs.img All dracut based live iso's use either squashfs.img (compressed live) or rootfs.img (uncompressed live).
Remove support for ext3fs.img.

/init: 9: /var/lib/dracut/hooks/pre-pivot/01-adduser.sh: cannot create /sysroot/
/init: 19: /var/lib/dracut/hooks/pre-pivot/01-adduser.sh: cannot create /sysroot/
chmod: cannot access '/sysroot/etc/default/live.conf': No such file or directory
grep: /sysroot/etc/shells: No such file or directory
/init: 23: /var/lib/dracut/hooks/pre-pivot/01-adduser.sh: cannot create /sysroot/
chroot: failed to run command '/bin/sh': No such file or directory
chroot: failed to run command 'useradd': No such file or directory
chroot: failed to run command 'sh': No such file or directory
chroot: failed to run command 'sh': No such file or directory
/init: 11: /var/lib/dracut/hooks/pre-pivot/03-locale.sh: cannot create /sysroot/
/init: 12: /var/lib/dracut/hooks/pre-pivot/03-locale.sh: cannot create /sysroot/
dracut Warning: Kernel command line option 'rd.live.overlay.overlayfs' is deprec
Cannot find init!
Please check to make sure you passed a valid root filesystem!

dracut Warning: 

Generating "/run/initramfs/rdsosreport.txt"
[    8.954837] I/O error, dev fd0, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 p
You might want to save "/run/initramfs/rdsosreport.txt" to a USB stick or /boot
after mounting them and attach it to a bug report.

To get more debug information in the report,
reboot with "rd.debug" added to the kernel command line.

Dropping to debug shell.

dracut:/#

Due to the dracut package being updated, you need to rename ext3fs.img to rootfs.img to avoid issues.

You can keep using mkfs.ext3 without any issues; just change the name of the img file so it works.