Adds os-keypairs to the core list for the V3 API.
Rename os-keypairs to keypairs as part of this change.
Fixes some incorrect urls in test_keypairs which still included
the tenant id
Updates api samples for servers since keypairs is now core and forms
part of the response by default
+DocImpact
Partially implements blueprint nova-v3-api
Change-Id: I8cdf52be0c8b19f7704848029a78373da8018cab
350d6f5337