locking: fix a few small issues uncovered by -Wthread-safety

- rpcwallet: No need to lock twice here
- openssl: Clang doesn't understand selective lock/unlock here. Ignore it.
- CNode: Fix a legitimate (though very unlikely) locking bug.

src/net.cpp

@@ -2033,8 +2033,10 @@ void CNode::EndMessage() UNLOCK_FUNCTION(cs_vSend)
         Fuzz(GetArg("-fuzzmessagestest", 10));
 
     if (ssSend.size() == 0)
+    {
+        LEAVE_CRITICAL_SECTION(cs_vSend);
         return;
-
+    }
     // Set the size
     unsigned int nSize = ssSend.size() - CMessageHeader::HEADER_SIZE;
     WriteLE32((uint8_t*)&ssSend[CMessageHeader::MESSAGE_SIZE_OFFSET], nSize);

src/util.cpp

@@ -113,7 +113,7 @@ CTranslationInterface translationInterface;
 
 /** Init OpenSSL library multithreading support */
 static CCriticalSection** ppmutexOpenSSL;
-void locking_callback(int mode, int i, const char* file, int line)
+void locking_callback(int mode, int i, const char* file, int line) NO_THREAD_SAFETY_ANALYSIS
 {
     if (mode & CRYPTO_LOCK) {
         ENTER_CRITICAL_SECTION(*ppmutexOpenSSL[i]);

src/wallet/rpcwallet.cpp

@@ -476,7 +476,6 @@ Value listaddressgroupings(const Array& params, bool fHelp)
             addressInfo.push_back(CBitcoinAddress(address).ToString());
             addressInfo.push_back(ValueFromAmount(balances[address]));
             {
-                LOCK(pwalletMain->cs_wallet);
                 if (pwalletMain->mapAddressBook.find(CBitcoinAddress(address).Get()) != pwalletMain->mapAddressBook.end())
                     addressInfo.push_back(pwalletMain->mapAddressBook.find(CBitcoinAddress(address).Get())->second.name);
             }