Report NIC link status via netlink carrier state

Update Redfish to use a DBus boolean value specifically intended for
communicating the NIC link state. Existing Intel server boards have a
NCSI channel with a speed value always assigned to 100Mbps. This makes
identifying link state impossible via the network speed value. The
DBus boolean uses the netlink carrier on/off state which is more
accurate.

Tested:

BMC Console commands:
ip link set down dev eth0
Get managers/bmc/eth0 state   ;; LinkStatus is LinkDown

ip link set up dev eth0
Get managers/bmc/eth0 state   ;; LinkStatus is LinkUp

Remove NIC cable from RJ45 connector
Get managers/bmc/eth0 state   ;; LinkStatus is LinkDown

Insert NIC cable into RJ45 connector
Get managers/bmc/eth0 state   ;; LinkStatus is LinkUp

Change-Id: I93d3f716a0afc563e3312e99b4a4163187985521
Signed-off-by: Johnathan Mantey <johnathanx.mantey@intel.com>