Convert v3 console plugin to v2.1

This patch changes v3 console plugin to v2.1 and makes v2
unit tests share between v2 and v2.1.

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

This patch also fix below issue in V2.1 console plugin-
 -  Remove try catch of 'InstanceNotFound' exception from V2.1
    console->index. This returns empty dict if non-existent server
    is specified. DB does not raise 'InstanceNotFound' exception.

Partially implements blueprint v2-on-v3-api

Change-Id: I306712f47457843c94e6441c4b9db7bf477c394c
Merge "Convert v3 console plugin to v2.1"