Pass rule modification errors back to CommandListener.

Change-Id: If01334dccad8b6230648713a57fd58be180ac66b
diff --git a/server/NetworkController.h b/server/NetworkController.h
index 4e93fa1..869f593 100644
--- a/server/NetworkController.h
+++ b/server/NetworkController.h
@@ -59,11 +59,11 @@
 
     bool createNetwork(unsigned netId, Permission permission);
     bool destroyNetwork(unsigned netId);
-    bool addInterfaceToNetwork(unsigned netId, const char* interface);
-    bool removeInterfaceFromNetwork(unsigned netId, const char* interface);
+    int addInterfaceToNetwork(unsigned netId, const char* interface);
+    int removeInterfaceFromNetwork(unsigned netId, const char* interface);
 
-    bool setPermissionForUser(Permission permission, const std::vector<unsigned>& uid);
-    bool setPermissionForNetwork(Permission permission, const std::vector<unsigned>& netId);
+    void setPermissionForUser(Permission permission, const std::vector<unsigned>& uid);
+    int setPermissionForNetwork(Permission permission, const std::vector<unsigned>& netId);
 
     // Routes are added to tables determined by the interface, so only |interface| is actually used.
     // |netId| is given only to sanity check that the interface has the correct netId.