[call-graph scheduling] fix bug in node removal

Summary:
The order was wrong: the map from procnames to node-ids was cleaned first, but to clean the map from node-ids to nodes, we need the id and we have already removed it.

The symptom was that effectively no new leaves are created by "removing" a node, so the call graph scheduler quickly devolves to the file-based one.

Reviewed By: skcho

Differential Revision: D18448209

fbshipit-source-id: f272a8112

infer/src/backend/CallGraph.ml

@@ -71,8 +71,8 @@ let n_procs {node_map} = NodeMap.length node_map
 let node_of_procname g pname = id_of_procname g pname |> Option.bind ~f:(node_of_id g)
 
 let remove (g : t) pname =
-  IdMap.remove g.id_map pname ;
+  id_of_procname g pname |> Option.iter ~f:(NodeMap.remove g.node_map) ;
-  id_of_procname g pname |> Option.iter ~f:(NodeMap.remove g.node_map)
+  IdMap.remove g.id_map pname
 
 
 let get_or_set_id ({id_map} as graph) procname =