resize: Add progress bar to virt-resize.
With this commit you will see a plain progress bar during the
lengthy copy operations, similar to below:
Summary of changes:
/dev/sda1: partition will be left alone
/dev/sda2: partition will be resized from 7.5G to 9.5G
/dev/sda2: content will be expanded using the 'pvresize' method
Copying /dev/sda1 ...
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Copying /dev/sda2 ...
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