server: Add UnavailableCommandException at ExceptionErrorCodeMap (#4926)

This PR proposes adding Exception UnavailableCommandException at the ExceptionErrorCodeMap

Author: GabrielBrascher

utils/src/main/java/com/cloud/utils/exception/CSExceptionErrorCode.java

@@ -70,6 +70,7 @@ public class CSExceptionErrorCode {
             ExceptionErrorCodeMap.put("com.cloud.async.AsyncCommandQueued", 4540);
             ExceptionErrorCodeMap.put("com.cloud.exception.RequestLimitException", 4545);
             ExceptionErrorCodeMap.put("com.cloud.exception.StorageConflictException", 4550);
+            ExceptionErrorCodeMap.put("com.cloud.exception.UnavailableCommandException", 4555);
 
             // Have a special error code for ServerApiException when it is
             // thrown in a standalone manner when failing to detect any of the above