Discover/Import Servers Inventory and hardware info to CFM

# 1. Introduction
Contrail Fabric Manager supports discovery and ZTP of network devices. To properly configure underlay for the infrastructure servers (controller/computes), CFM needs to know about the connection details of servers and switch ports. Also for baremetal workload, details about the baremetal hardware needs to added manually as of now. In case of ZTP, discovery of servers and auto-adding them to contrail-command should be provided.

# 2. Problem Statement
Adding Servers for provisioing contrail or adding baremetal nodes to Contrail-Command is a manual task as of now. with 100 of infra
nodes/baremetal nodes to add, it become cumbersome to use UI. Also for baremetal nodes, all hardware detail needs to be known and has to be entered.

So there is requirement to automate this portion of the ZTP and discover all possible servers

### Use Case:
Server Discovery will enhance the capabilities of the Contrail Fabric Manager to auto-add the servers and its hardware details, network connections, capabilities to contrail-command. Also with possible integration of contrail-command with RHSOP/ironic, this may be used for re-imaging the servers and bringing the servers with needed OS to provision controller and
computes. Also this will provide connection details of baremetals to Fabric Manager, which will configure the switches for providing underlay connectivity.