[baremetal] idf for opnfv_vm and update the pdf

[baremetal] idf for opnfv_vm and update the pdf

Physical hardware PODs provide a pdf and a idf to describe hardware and other
information (e.g. what is the purpose for each interface). To reuse the
same code for opnfv vm and also become consistent, we should also describe
the opnfv vm with an idf and a pdf. This patch simplifies what needs to
be done for baremetal, especially for this (future) patch:

https://gerrit.opnfv.org/gerrit/#/c/60797/11

As we add an idf, we should update dynamic_inventory and how we create
the opnfv vm. Obviously, he opnfv_vm.yml gets removed.

Change-Id: I930728474631fc214e4a9adc8581e0c16d230176
Signed-off-by: Manuel Buil <mbuil@suse.com>