Improve robustness with localbuilding

shutil.move will fail if the target already exists, thus delete
the target file if it exists.

Also, add a bit more debug output.

Change-Id: Ie58dfe1806e0aedf60c07bc7e7c8bbb44a948fee
Improve cli output

Implement some suggestions from Summer (see
https://review.openstack.org/#/c/73476)
and enhance.

Fix parsing of options, shown in output of "cinder --metadata".

Change-Id: I3a330dbdad0439c2785d6da141eadc63c550848e
Merge "Improve robustness with localbuilding"