identification: Set possible answers to same msgid

This patch is actually part of NEO MR nexedi/neoppod!20.
In the context of the WWM/wind branch this patch is cherry-picked in order
to accelerate our WC2 real-world testing affords on our WWM/wind clone.
Even if we don't use this patch as an actual solution, it helps here to
early test NEO/go bits of kirr/neo!2.

neo/master/handlers/identification.py

@@ -156,5 +156,5 @@ class SecondaryIdentificationHandler(EventHandler):
             for node in app.nm.getMasterList()]
         conn.send(Packets.NotPrimaryMaster(
             primary and known_master_list.index(primary),
-            known_master_list))
+            known_master_list), msg_id=conn.peer_id)
         conn.abort()