TestableModeAccessorDecorator: Fix doPreRead

Lock is only released for accessors with wait_for_new_data on blocking
reads. This fixes usage of readLatest() in testable mode.

include/TestableModeAccessorDecorator.h

@@ -113,14 +113,14 @@ namespace ChimeraTK {
       if(Application::testableModeTestLock()) Application::testableModeUnlock("doReadTransfer " + this->getName());
     }
 
-    /** Implement callback called by TransferFuture before it blocks in wait() */
-    // TODO Removed in TE spec. Call preRead isntead, see F.4 Still, has to
-    // handle multiple calls to preRead in readAny()
     void doPreRead(TransferType type) override {
-      if(_handleRead) {
+      _target->preRead(type);
+
+      // Blocking reads have to release the lock so the data transport can happen
+      if(_handleRead && type == TransferType::read &&
+          TransferElement::_accessModeFlags.has(AccessMode::wait_for_new_data)) {
         releaseLock();
       }
-      _target->preRead(type);
     }
 
     /** Obtain the testableModeLock if not owned yet, and decrement the counter.