a) Enable LLDP for Host namespace for Management Port
b) Make sure Management IP is avaliable in per asic namespace
   needed for LLDP Chassis configuration
c) Make sure chassis mac-address is correct in per asic namespace
d) Do not run lldp on eth0 of per asic namespace and avoid chassis
   configuration for same
e) Use Linux hostname instead from Device Metadata for lldp chassis
   configuration since in multi-npu platforms device metadata hostname
   will be differnt

Signed-off-by: Abhishek Dosi <abdosi@microsoft.com>

a) Use Device Metadata hostname even in per namespace conatiner.
   updated minigraph parsing for same to have hostname as system
   hostname and add new key for asic name

b) Minigraph changes to have MGMT_INTERFACE Key in per asic/namespace
   config also as needed for LLDP for setting chassis management IP.

Signed-off-by: Abhishek Dosi <abdosi@microsoft.com>