validation: don't clear cache on periodic flush

Author: andrewtoth

src/validation.cpp

@@ -2745,8 +2745,10 @@ bool Chainstate::FlushStateToDisk(
                 return FatalError(m_chainman.GetNotifications(), state, _("Disk space is too low!"));
             }
             // Flush the chainstate (which may refer to block index entries).
-            if (!CoinsTip().Flush())
+            const auto empty_cache{(mode == FlushStateMode::ALWAYS) || fCacheLarge || fCacheCritical || fFlushForPrune};
+            if (empty_cache ? !CoinsTip().Flush() : !CoinsTip().Sync()) {
                 return FatalError(m_chainman.GetNotifications(), state, _("Failed to write to coin database."));
+            }
             m_last_flush = nNow;
             full_flush_completed = true;
             TRACE5(utxocache, flush,