cover DisconnectBlock with lock annotation

CoinsTip() access requires cs_main and therefore so should this function.

src/validation.cpp

@@ -1485,6 +1485,7 @@ int ApplyTxInUndo(Coin&& undo, CCoinsViewCache& view, const COutPoint& out)
  *  When FAILED is returned, view is left in an indeterminate state. */
 DisconnectResult CChainState::DisconnectBlock(const CBlock& block, const CBlockIndex* pindex, CCoinsViewCache& view)
 {
+    AssertLockHeld(::cs_main);
     bool fClean = true;
 
     CBlockUndo blockUndo;