don't override start() method

ZcashLightClientKit/Block/Processor/CompactBlockDownloadOperation.swift

@@ -30,6 +30,7 @@ class CompactBlockDownloadOperation: ZcashOperation {
             cancel()
             return
         }
+        self.startedHandler?()
         do {
             try downloader.downloadBlockRange(range)
         } catch {
@@ -78,6 +79,7 @@ class CompactBlockStreamDownloadOperation: ZcashOperation {
             cancel()
             return
         }
+        self.startedHandler?()
         do {
             
             if self.targetHeight == nil {
@@ -178,6 +180,7 @@ class CompactBlockBatchDownloadOperation: ZcashOperation {
             cancel()
             return
         }
+        self.startedHandler?()
         do {
             
             guard startHeight > ZcashSDK.SAPLING_ACTIVATION_HEIGHT else {

ZcashLightClientKit/Block/Processor/CompactBlockEnhancementOperation.swift

@@ -49,7 +49,7 @@ class CompactBlockEnhancementOperation: ZcashOperation {
             cancel()
             return
         }
-        
+        self.startedHandler?()
         // fetch transactions
         
         do {

ZcashLightClientKit/Block/Processor/CompactBlockScanningOperation.swift

@@ -32,6 +32,7 @@ class CompactBlockScanningOperation: ZcashOperation {
             cancel()
             return
         }
+        self.startedHandler?()
         guard self.rustBackend.scanBlocks(dbCache: self.cacheDb, dbData: self.dataDb, limit: limit) else {
             self.error = self.rustBackend.lastError() ?? ZcashOperationError.unknown
             LoggerProxy.debug("block scanning failed with error: \(String(describing: self.error))")
@@ -134,6 +135,7 @@ class CompactBlockBatchScanningOperation: ZcashOperation {
             cancel()
             return
         }
+        self.startedHandler?()
         do {
             if batchSize == 0 {
                 let scanStartTime = Date()

ZcashLightClientKit/Block/Processor/CompactBlockValidationInformation.swift

@@ -35,6 +35,7 @@ class CompactBlockValidationOperation: ZcashOperation {
             cancel()
             return
         }
+        self.startedHandler?()
         let result = self.rustBackend.validateCombinedChain(dbCache: cacheDb, dbData: dataDb)
         switch result {
         case 0:

ZcashLightClientKit/Block/Processor/FetchUnspentTxOutputsOperation.swift

@@ -41,8 +41,7 @@ class FetchUnspentTxOutputsOperation: ZcashOperation {
             cancel()
             return
         }
-        
-      
+        self.startedHandler?()
         do {
             let tAddresses = try accountRepository.getAll().map({ $0.transparentAddress })
             do {

ZcashLightClientKit/Block/Processor/ZcashOperation.swift

@@ -38,12 +38,7 @@ class ZcashOperation: Operation {
         self.handlerDispatchQueue = completionDispatchQueue
     }
     
-    override func start() {
-        LoggerProxy.debug("\(self) started")
-        super.start()
-        guard !shouldCancel() else { return }
-        startedHandler?()
-    }
+    
     
     func shouldCancel() -> Bool {
         self.error != nil || isCancelled || dependencyCancelled()