Port offline node fixes from Rapi to IAllocator

The IAllocator source was copied from Rapi before the offline node fixes
were made. This changes such that offline nodes are accepted correctly.

Ganeti/HTools/IAlloc.hs

@@ -64,15 +64,19 @@ parseInstance ktn n a = do
 parseNode :: String -> JSObject JSValue -> Result (String, Node.Node)
 parseNode n a = do
     let name = n
-    mtotal <- fromObj "total_memory" a
-    mnode <- fromObj "reserved_memory" a
-    mfree <- fromObj "free_memory" a
-    dtotal <- fromObj "total_disk" a
-    dfree <- fromObj "free_disk" a
     offline <- fromObj "offline" a
     drained <- fromObj "drained" a
-    return $ (name, Node.create n mtotal mnode mfree dtotal dfree
-                      (offline || drained))
+    node <- (case offline of
+               True -> return $ Node.create name 0 0 0 0 0 True
+               _ -> do
+                 mtotal <- fromObj "total_memory" a
+                 mnode <- fromObj "reserved_memory" a
+                 mfree <- fromObj "free_memory" a
+                 dtotal <- fromObj "total_disk" a
+                 dfree <- fromObj "free_disk" a
+                 return $ Node.create n mtotal mnode mfree
+                        dtotal dfree (offline || drained))
+    return (name, node)
 
 parseData :: String -> Result Request
 parseData body = do