docs: Add 1.5.0 to prior release notes
docs: Add 1.5.0 to prior release notes

Change-Id: Idc6ac068161a3ead277b9c04170d80f88a55b405
Reviewed-on: http://gerrit.cloudera.org:8080/8722
Reviewed-by: Mike Percy <e07a1fd797b473a9c849e618aa2ce06d8055760b@apache.org>
Tested-by: Mike Percy <e07a1fd797b473a9c849e618aa2ce06d8055760b@apache.org>

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