[leapp] Ensure that there is enough diskspace in /var/lib/leapp/scratch/diskimages/root_boot at least XXX mib are needed

Issue

• Leapp upgrade fails with below error:

  2023-11-16 22:34:25.960577 [ERROR] Actor: target_userspace_creator
  Message: Failed to execute command `/bin/dd if=/dev/zero of=/var/lib/leapp/scratch/diskimages/root_ bs=1M count=0 seek=21380`. Error: Command ['/bin/dd', 'if=/dev/zero', 'of=/var/lib/leapp/scratch/diskimages/root_', 'bs=1M', 'count=0', 'seek=21380'] failed with exit code 1.
  Summary:
      Please ensure that there is enough diskspace on the partition hostingthe /var/lib/leapp/scratch/diskimages directory.: Please ensure that there is enough diskspace on the partition hostingthe /var/lib/leapp/scratch/diskimages directory.
  

Note:The value of seek could vary. It was observed to be 2GB in one run of leapp while it was 21GB in another.