Port server_diagnostics extension to v3 API Part2

Ports the server_diagnostics extensions and the corresponding
unittests to the v3 framework.

Partially implements blueprint nova-v3-api

Change-Id: I2ddf626a539d47884e845d73ec67e9f9169dcb2b
Merge "Port server_diagnostics extension to v3 API Part2"
Merge remote-tracking branch 'm_src_repo/citrix-fixes' into build-temp