Prevent unconditionally writing over the LinkStatus

The NIC LinkStatus was being assigned a LinkUp or NoLink value
depending on whether the NIC is enabled.

Subsequent code unconditionally overwrites the LinkStatus.

The LinkStatus needs to take into account the NIC enabled state as
well as the link up/down state.

Tested:
Confirmed NIC enabled/link active resulted in LinkUp.
Confrimed NIC enabled/no-carrier resulted in LinkDown.
Connfimred NIC disable resulted in NoLink.

Change-Id: Iece3686cac9714e427b0e100f486a4ced334f7af
Signed-off-by: Johnathan Mantey <johnathanx.mantey@intel.com>