Define Errors on CurrentOperatingConfig properties

There are some conditions which would prevent changes to the
CurrentOperatingConfig interface on a CPU. To make it easier for a user
to know their property Set was rejected, define some common error codes
to return.

Signed-off-by: Jonathan Doman <jonathan.doman@intel.com>
Change-Id: I7a1d3a8c0194a5c2f7b275d779915d2c2c72c530
diff --git a/xyz/openbmc_project/Common.errors.yaml b/xyz/openbmc_project/Common.errors.yaml
index d365b35..288aa7c 100644
--- a/xyz/openbmc_project/Common.errors.yaml
+++ b/xyz/openbmc_project/Common.errors.yaml
@@ -14,3 +14,5 @@
   description: Too many resources have already been granted.
 - name: ResourceNotFound
   description: The resource is not found.
+- name: Unavailable
+  description: The service is temporarily unavailable.