Filter endpoints by region whenever possible

Previously, the endpoints command just returned the first endpoint. This
was not very useful; people expected to see the endpoints in the region
they specified. This patch does the following:

- If there's only one endpoint, use that.
- If there's a specific one for your region, use that.
- If there isn't, warn, and show the other ones.

Closes-Bug: #1256009
Change-Id: I70b82bdffb9b2e3da415a3bb941bcff287e39789
fix host resource repr to use 'host' attribute

This change fixes an AttributeError raised when attempting to
represent a host resource as a string.

Change-Id: I33369b20ed7f5219c3b507107b8f3a37b46eacee
Closes-Bug: #1327005
Merge "Filter endpoints by region whenever possible"
Merge "fix host resource repr to use 'host' attribute"