Fix i18n messages in novaclient, part I

This change make all the text visible by the user i18n. The
messages changes are in prints, logs, exceptions, helps, etc
Pep8 errors about "Multiple positional placeholders" also fixed

Change-Id: I731afea790baddbc34d059b93a35e3d275fc1df8
Merge "Fix i18n messages in novaclient, part I"