[net] Make CNode msg process queue members private

Now that all access to the process queue members is handled by methods
of `CNode` we can make these members private.

Author: dergoegge

src/net.h

@@ -376,10 +376,6 @@ class CNode
     Mutex m_sock_mutex;
     Mutex cs_vRecv;
 
-    RecursiveMutex cs_vProcessMsg;
-    std::list<CNetMessage> vProcessMsg GUARDED_BY(cs_vProcessMsg);
-    size_t nProcessQueueSize GUARDED_BY(cs_vProcessMsg){0};
-
     uint64_t nRecvBytes GUARDED_BY(cs_vRecv){0};
 
     std::atomic<std::chrono::seconds> m_last_send{0s};
@@ -619,6 +615,10 @@ class CNode
 
     std::list<CNetMessage> vRecvMsg; // Used only by SocketHandler thread
 
+    RecursiveMutex cs_vProcessMsg;
+    std::list<CNetMessage> vProcessMsg GUARDED_BY(cs_vProcessMsg);
+    size_t nProcessQueueSize GUARDED_BY(cs_vProcessMsg){0};
+
     // Our address, as reported by the peer
     CService addrLocal GUARDED_BY(m_addr_local_mutex);
     mutable Mutex m_addr_local_mutex;