Use the server name attribute

The 'show' attribute results in a nova API call, which has
performance overhead even with attribute memoization.
The name attribute was added to expose the name without needing
an API call, since the resource already knows the name. This
change switches from using 'show' to 'name' throughout.

Change-Id: I1e83dd008cd02e5cec97868db0d5a695f07b7199