CBQE-1291 remove uncomplete offline upgrade spec

Change-Id: I577e176ddb61f5563fc5bc70abc4aca931535408
Reviewed-on: http://review.couchbase.org/26933
Reviewed-by: Chisheng Hong <chisheng@couchbase.com>
Tested-by: Chisheng Hong <chisheng@couchbase.com>