HDFS-16068. WebHdfsFileSystem has a possible connection leak in connection with HttpFS (#3104)

(cherry picked from commit 839fcf7682270bc6ba151875549d64d81917f425)

hadoop-hdfs-project/hadoop-hdfs-client/src/main/java/org/apache/hadoop/hdfs/web/WebHdfsFileSystem.java

@@ -2277,10 +2277,12 @@ public class WebHdfsFileSystem extends FileSystem
     @VisibleForTesting
     void closeInputStream(RunnerState rs) throws IOException {
       if (in != null) {
-        IOUtils.close(cachedConnection);
         in = null;
       }
-      cachedConnection = null;
+      if (cachedConnection != null) {
+        IOUtils.close(cachedConnection);
+        cachedConnection = null;
+      }
       runnerState = rs;
     }