Fix for "nova help list" command

The output of "nova help list" shows several argument as "Admin Only",
when they are not.
This patch modifies help notes for --ip, --ip6 and --instance-name,
which can be used by regular users.

DocImpact

Change-Id: Iac541ac8e698a27348b437ad53910bd09ea7f257
Closes-Bug: #1295126
Merge "Fix for "nova help list" command"