v2v: Print mountpoint stats in debugging output.

Useful for debugging speed / fstrim issues.
v2v: Print virtual and real copying rates.

Useful to diagnose speed issues in the qemu block drivers.
v2v: Fix the --no-trim option so it works.

We never updated the no_trim variable in the case where this option
was supplied, so it never did anything, proving once again that unless
you have a test case, the feature won't work.
v2v: Enable trimming of data disks and non-mountpoints (RHBZ#1150701).

This also modifies the --no-trim option so you can specify a device
name, since this is necessary if fstrim can apply to non-mountpoints.