Add UnavailableOffline state mapping and add getResourceStatus helper

[jnin-dev]

1. Added a utility function to reduce code duplication for retrieving
   resource's Status.State and Status.Health
2. Mapped D-Bus Available to Redfish UnavailableOffline

Tested:

• Build successfully
• Unit tests passed
• Sent requests and received Status.State and Status.Health as expected
  with the new mapping

curl -k -v https://${bmc}/redfish/v1/Systems/system/Processors/mcm/SubProcessors/core0

Results with

{
  "@odata.id": "/redfish/v1/Systems/system/Processors/mcm/SubProcessors/core0",
  "@odata.type": "#Processor.v1_18_0.Processor",
  "Enabled": true,
  "Id": "core0",
  "Name": "Node 0 processor module Core 0",
  "Status": {
    "Health": "OK",
    "State": "UnavailableOffline"
 }

[jeaaustx]

Overall the change looks reasonable to me. I have a few comments in the code and a couple of comments on the commit messages:

• The utils function commit message talks about UnavailableOffline but the output example in the commit message only shows Absent. For clarity it would be good to show the different cases in the output in the commit message.
• I'm wondering about carrying these patches and the ease of handling rebasing in the future. I suggest considering breaking these up to a single commit that adds the utility function and then separate commits for each of the places changing to use the utility function. (This would help with chicken/egg problem on rebase of needing support in place that pulls in the utility function for any other commits dependant on the function.) But...
• Is this going upstream? If so then above concern about rebase is less important. However for upstream it is still easiest to get the utility function commit in by itself.
• Probably should add some unit tests for the utiilty function.

[jnin-dev]

The utils function commit message talks about UnavailableOffline but the output example in the commit message only shows Absent. For clarity it would be good to show the different cases in the output in the commit message.

I added to the commit message about the difference cases for Status.State

I'm wondering about carrying these patches and the ease of handling rebasing in the future. I suggest considering breaking these up to a single commit that adds the utility function and then separate commits for each of the places changing to use the utility function.

I believe the utility function will go upstream. I've separated them into different commits for each resource since it'll be cleaner

Probably should add some unit tests for the utiilty function.

Done.

[jeaaustx]

Changes look good to me. I have just the one comment about the refactoring.