refactor: CTxMemPool::ApplyDelta() requires CTxMemPool::cs lock

No change in behavior, the lock is already held at call sites.
Also `const uint256` refactored to `const uint256&`.

Author: hebasto

src/txmempool.cpp

@@ -852,9 +852,9 @@ void CTxMemPool::PrioritiseTransaction(const uint256& hash, const CAmount& nFeeD
     LogPrintf("PrioritiseTransaction: %s feerate += %s\n", hash.ToString(), FormatMoney(nFeeDelta));
 }
 
-void CTxMemPool::ApplyDelta(const uint256 hash, CAmount &nFeeDelta) const
+void CTxMemPool::ApplyDelta(const uint256& hash, CAmount &nFeeDelta) const
 {
-    LOCK(cs);
+    AssertLockHeld(cs);
     std::map<uint256, CAmount>::const_iterator pos = mapDeltas.find(hash);
     if (pos == mapDeltas.end())
         return;

src/txmempool.h

@@ -626,7 +626,7 @@ class CTxMemPool
 
     /** Affect CreateNewBlock prioritisation of transactions */
     void PrioritiseTransaction(const uint256& hash, const CAmount& nFeeDelta);
-    void ApplyDelta(const uint256 hash, CAmount &nFeeDelta) const;
+    void ApplyDelta(const uint256& hash, CAmount &nFeeDelta) const EXCLUSIVE_LOCKS_REQUIRED(cs);
     void ClearPrioritisation(const uint256 hash);
 
     /** Get the transaction in the pool that spends the same prevout */