p2p: Unify Send and Receive protocol versions

There is no change in behavior on the P2P network.

src/net.h

@@ -827,7 +827,6 @@ public:
 
     std::deque<CInv> vRecvGetData;
     uint64_t nRecvBytes GUARDED_BY(cs_vRecv){0};
-    std::atomic<int> nRecvVersion{INIT_PROTO_VERSION};
 
     std::atomic<int64_t> nLastSend{0};
     std::atomic<int64_t> nLastRecv{0};
@@ -1014,6 +1013,7 @@ private:
     const NodeId id;
     const uint64_t nLocalHostNonce;
     const ConnectionType m_conn_type;
+    std::atomic<int> m_greatest_common_version{INIT_PROTO_VERSION};
 
     //! Services offered to this peer.
     //!
@@ -1033,7 +1033,6 @@ private:
     const ServiceFlags nLocalServices;
 
     const int nMyStartingHeight;
-    int nSendVersion{0};
     NetPermissionFlags m_permissionFlags{ PF_NONE };
     std::list<CNetMessage> vRecvMsg;  // Used only by SocketHandler thread
 
@@ -1065,16 +1064,14 @@ public:
 
     bool ReceiveMsgBytes(const char *pch, unsigned int nBytes, bool& complete);
 
-    void SetRecvVersion(int nVersionIn)
+    void SetCommonVersion(int greatest_common_version)
     {
-        nRecvVersion = nVersionIn;
+        m_greatest_common_version = greatest_common_version;
     }
-    int GetRecvVersion() const
+    int GetCommonVersion() const
     {
-        return nRecvVersion;
+        return m_greatest_common_version;
     }
-    void SetSendVersion(int nVersionIn);
-    int GetSendVersion() const;
 
     CService GetAddrLocal() const;
     //! May not be called more than once