transaction: remove unused StatusTransactionCompletionCallback
transaction: remove unused StatusTransactionCompletionCallback

This has been unused since 899bde406ef16e84b930c7232ba9b25e7fab44f6.

Change-Id: Ie3345b459637f170808e0d73c12a6754c6c2da31
Reviewed-on: http://gerrit.cloudera.org:8080/7632
Reviewed-by: Alexey Serbin <864f6b82bd94e8dda64141d4274519ee66e0102e@cloudera.com>
Tested-by: Kudu Jenkins
Reviewed-by: David Ribeiro Alves <dbbafdb4f25eb0c1ff3facf0e5f2f27705055af1@gmail.com>

InspurUSA/kudu,InspurUSA/kudu,andrwng/kudu,andrwng/kudu,EvilMcJerkface/kudu,cloudera/kudu,helifu/kudu,InspurUSA/kudu,andrwng/kudu,EvilMcJerkface/kudu,cloudera/kudu,andrwng/kudu,EvilMcJerkface/kudu,helifu/kudu,cloudera/kudu,InspurUSA/kudu,cloudera/kudu,cloudera/kudu,EvilMcJerkface/kudu,cloudera/kudu,InspurUSA/kudu,InspurUSA/kudu,EvilMcJerkface/kudu,cloudera/kudu,EvilMcJerkface/kudu,helifu/kudu,andrwng/kudu,helifu/kudu,EvilMcJerkface/kudu,helifu/kudu,cloudera/kudu,helifu/kudu,EvilMcJerkface/kudu,InspurUSA/kudu,andrwng/kudu,EvilMcJerkface/kudu,cloudera/kudu,InspurUSA/kudu,helifu/kudu,andrwng/kudu,InspurUSA/kudu,andrwng/kudu,helifu/kudu,helifu/kudu,andrwng/kudu