Only send one GetAddr response per connection.

src/net.h

@@ -355,6 +355,7 @@ public:
     // b) the peer may tell us in its version message that we should not relay tx invs
     //    unless it loads a bloom filter.
     bool fRelayTxes; //protected by cs_filter
+    bool fSentAddr;
     CSemaphoreGrant grantOutbound;
     CCriticalSection cs_filter;
     CBloomFilter* pfilter;