state: Add Available mapping for Fabric Adapters

- Utilized resource util's getResourceState and getResourceHealth to
  get the Status.State and Status.Health of the fabric adapters resource
- Map `Available` to Redfish `UnavailableOffline`

Tested:
- Unit tests passed
- Redfish Service Validator passed
```
curl -k -v https://${bmc}/redfish/v1/Systems/system/FabricAdapters/pcie_card0
```
Results in
```
{
  "@odata.id": "/redfish/v1/Systems/system/FabricAdapters/pcie_card0",
  "@odata.type": "#FabricAdapter.v1_4_0.FabricAdapter",
  ...
  "Status": {
    "Health": "OK",
    "State": "UnavailableOffline"
  }
  ...
}
```
If the resource is functional and present but not available

Change-Id: I045191029ba0f08d1eccb2bf4406cd4925289459
Signed-off-by: Justin Nguyen <justinnanguyen@gmail.com>