This interface will be used by executors and other
commands to interact with remote hosts.
It is split into generic inventory and BaremetalInventory to
keep open door for cloud providers. In the future, if we
decide to that we need, for example list VMs in google, azure,
openstack or any other clouds, we would extend inventory interface
with approprate more sepcific inventory such as OpenstackInventory
etc...
Relates-To: #297
Change-Id: Ie19ed6047390e09a658c1e943b5e83d88e9668bf
d05579b4a4