rpc/*,rest: Add review-only assertion to EnsureChainman

src/rpc/blockchain.cpp

@@ -79,6 +79,7 @@ ChainstateManager& EnsureChainman(const std::any& context)
     if (!node.chainman) {
         throw JSONRPCError(RPC_INTERNAL_ERROR, "Node chainman not found");
     }
+    WITH_LOCK(::cs_main, CHECK_NONFATAL(std::addressof(g_chainman) == std::addressof(*node.chainman)));
     return *node.chainman;
 }