javelin-resources: attach a volume to a server

In tempest/javelin2, we want to attach a volume to a server. For that we
need to bind the attachment in the resources.yaml.
Also, adding another volume to be sure we can create 2 volumes and
attach them to 2 differents instances.

Prereq for blueprint:javelin2
Change-Id: I71be5c0a2af69706f38f9f3a049d5591d838d8c0
Signed-off-by: Emilien Macchi <emilien.macchi@enovance.com>