Fixed: custom field values on devices (properties) + some pep8 cleaning.
Code review fixes + property value gets deleted when it gets its default
value back.
Code review fix.
Merge pull request #656 from xor-xor/t1386

Fixed: custom field values on devices (properties) + some pep8 cleaning.
Merge branch 'master' of github.com:allegro/ralph into ganeti
Code review corrections