HBASE--28666 Dropping unclosed WALTailingReaders leads to leaked sock…

…ets (#5994)

In WALEntryStream, always use current WALTailingReader if one exists 

Signed-off-by: Duo Zhang <zhangduo@apache.org>

hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/WALEntryStream.java

@@ -219,6 +219,7 @@ private HasNext prepareReader() {
             // we will read from the beginning so we should always clear the compression context
             reader.resetTo(-1, true);
           }
+          return HasNext.YES;
         } catch (IOException e) {
           LOG.warn("Failed to reset reader {} to pos {}, reset compression={}", currentPath,
             currentPositionOfEntry, state.resetCompression(), e);