Bug#538348: pkgsel/tasksel: can no longer determine free space for desktop task

[Frans Pop <elendil@planet.nl>]

Package: pkgsel
Version: 0.25

tasksel wants to do in the target chroot:
tasksel/tests/desktop:  disk=$(df -P /usr | tail -1 | awk '{print $4}')

But this fails with:
in-target: df:
in-target: Warning: cannot read table of mounted file systems
in-target: : No such file or directory

Probably related to the problem reported by Martin re. initramfs-tools:
an incorrect state of /etc/mtab in /target. It may also a result of the 
change Colin committed in debootstrap this week.