Add stop method stub

blockstore.cpp

@@ -194,6 +194,11 @@ void blockstore::loop()
     }
 }
 
+bool blockstore::stop()
+{
+    return false;
+}
+
 void blockstore::check_wait(blockstore_operation *op)
 {
     if (op->wait_for == WAIT_SQE)

blockstore.h

@@ -311,6 +311,11 @@ public:
     void handle_event(ring_data_t* data);
     void loop();
 
+    // Returns true when it's safe to destroy the instance. If destroying the instance
+    // requires to purge some queues, starts that process. Should be called in the event
+    // loop until it returns true.
+    bool stop();
+
     // Submission
     int enqueue_op(blockstore_operation *op);
 };