Translog: close channel on failures while converting a writer to a reader

TranslogWriter.closeIntoReader transfers the file ownership from a writer to a reader and closes the writer. If the transfer fails, we need to make sure we closed the underlying channel as the writer is already closes.

See: http://build-us-00.elastic.co/job/es_core_master_regression/4355

Relates to #16142

core/src/main/java/org/elasticsearch/index/translog/TranslogWriter.java

@@ -192,7 +192,13 @@ public class TranslogWriter extends BaseTranslogReader implements Closeable {
             throw e;
         }
         if (closed.compareAndSet(false, true)) {
+            try {
                 return new TranslogReader(generation, channel, path, firstOperationOffset, getWrittenOffset(), operationCounter);
+            } catch (Throwable t) {
+                // close the channel, as we are closed and failed to create a new reader
+                IOUtils.closeWhileHandlingException(channel);
+                throw t;
+            }
         } else {
             throw new AlreadyClosedException("translog [" + getGeneration() + "] is already closed (path [" + path + "]", tragedy);
         }