Change ViewBuilder into v2.1 for servers

This patch changes v3 servers' ViewBuilder to v2.1. And also
change related unittests and api sample tests.

The differences between v2 and v3 are described on the wiki page
https://wiki.openstack.org/wiki/NovaAPIv2tov3.

Partially implements blueprint v2-on-v3-api

Change-Id: Ie68d46daa91ef43c84eeef479c0986d5e7f15719
Change 'changes_since'/'changes-since' into v2.1 style for servers

This patch changes 'changes_since' to 'change-since' that same
with v2 api. And also change the related unittest.

The differences between v2 and v3 are described on the wiki page
https://wiki.openstack.org/wiki/NovaAPIv2tov3.

Partially implements blueprint v2-on-v3-api

Change-Id: If2a95827965bd6955b01190f2d4dd4fcd9c76dc9
Merge "Change ViewBuilder into v2.1 for servers"
Merge "Change 'changes_since'/'changes-since' into v2.1 style for servers"