HDFS-17062. HA NameNode Web UI should show last HA Transition time (#5791). Contributed by Zhaohui Wang.

Reviewed-by: Shilun Fan <slfan1989@apache.org>
Signed-off-by: Ayush Saxena <ayushsaxena@apache.org>

hadoop-hdfs-project/hadoop-hdfs/src/main/webapps/hdfs/dfshealth.html

@@ -196,6 +196,9 @@
 {#fsn}
   <tr><th>Last Checkpoint Time</th><td>{@if cond="{LastCheckpointTime} === 0"}Never{:else}{LastCheckpointTime|date_tostring}{/if}</td></tr>
 {/fsn}
+{#nnstat}
+  <tr><th>Last HA Transition Time</th><td>{@if cond="{LastHATransitionTime} === 0"}Never{:else}{LastHATransitionTime|date_tostring}{/if}</td></tr>
+{/nnstat}
 {#ecstat}
   <tr><th>Enabled Erasure Coding Policies</th><td>{EnabledEcPolicies}</td></tr>
 {/ecstat}