Increase threadsafety annotation coverage

src/qt/clientmodel.h

@@ -61,7 +61,7 @@ public:
     //! Return number of connections, default is in- and outbound (total)
     int getNumConnections(unsigned int flags = CONNECTIONS_ALL) const;
     int getNumBlocks() const;
-    uint256 getBestBlockHash();
+    uint256 getBestBlockHash() EXCLUSIVE_LOCKS_REQUIRED(!m_cached_tip_mutex);
     int getHeaderTipHeight() const;
     int64_t getHeaderTipTime() const;