[webui] drop 'Last status' column for tombstoned tablets
[webui] drop 'Last status' column for tombstoned tablets

This is a follow-up to 9a01205ce10b468698c76aedbf51016a90045620.

Change-Id: I5c21b9fbf7c6992c8cb29d9cc2d4c11623bbbbfa
Reviewed-on: http://gerrit.cloudera.org:8080/11972
Tested-by: Kudu Jenkins
Reviewed-by: Will Berkeley <c74686ab413a71926fc1bc9d16ebfa30e619336a@gmail.com>

helifu/kudu,helifu/kudu,InspurUSA/kudu,helifu/kudu,helifu/kudu,InspurUSA/kudu,InspurUSA/kudu,InspurUSA/kudu,helifu/kudu,InspurUSA/kudu,InspurUSA/kudu,helifu/kudu,helifu/kudu,helifu/kudu,InspurUSA/kudu,helifu/kudu,InspurUSA/kudu,InspurUSA/kudu