v2v: Introduce Types.mpstats struct storing mountpoint statistics.

This is just code refactoring.
v2v: Estimate the amount of space required on the target.

Estimate the amount of space required on the target by each source
disk after conversion.  The estimate is approximately a ceiling on
this, and actual use should be considerably lower.

Provide an extra output method (#check_target_free_space) which output
modules may use to check that there is sufficient free space to
proceed, before conversion starts.  None of the output modules
actually implement this at the moment.
v2v: Fix variable name usage_mb -> usage_gb.

It's actually storing usage in gigabytes, not megabytes.
v2v: -o rhev/vdsm: In --no-copy case, use estimate for ovf:actual_size (RHBZ#1140156).
appliance: Add comment with udev debugging option.
daemon: Run udev_settle after pwrite-device finishes (RHBZ#1141451).

When you call close on any block device, udev kicks off a rule which
runs blkid to reexamine the device.  We need to wait for this rule to
finish running since it holds the device open and can cause other
operations to fail, notably mkfs.

(cherry picked from commit a9c8123c72db47bcab8dd738e8d5256a9ae87f11)
Version 1.27.45.