refactor: use atomic to avoid blocking chainlocks cs on each call to cleanup

Author: PastaPastaPasta

src/llmq/chainlocks.cpp

@@ -617,11 +617,8 @@ void CChainLocksHandler::Cleanup()
         return;
     }
 
-    {
-        LOCK(cs);
-        if (GetTimeMillis() - lastCleanupTime < CLEANUP_INTERVAL) {
-            return;
-        }
+    if (GetTimeMillis() - lastCleanupTime < CLEANUP_INTERVAL) {
+        return;
     }
 
     // need mempool.cs due to GetTransaction calls

src/llmq/chainlocks.h

@@ -82,7 +82,7 @@ class CChainLocksHandler : public CRecoveredSigsListener
 
     std::map<uint256, int64_t> seenChainLocks GUARDED_BY(cs);
 
-    int64_t lastCleanupTime GUARDED_BY(cs) {0};
+    std::atomic<int64_t> lastCleanupTime{0};
 
 public:
     explicit CChainLocksHandler(CChainState& chainstate, CConnman& _connman, CMasternodeSync& mn_sync, CQuorumManager& _qman,