MB-100: Fix corner case in cbrecoverytests

Change-Id: Ib9a265f2a36b23048033a7866b72b786cd3bca58
Reviewed-on: http://review.couchbase.org/27186
Reviewed-by: abhinav dangeti <abhinav.dangeti@gmail.com>
Tested-by: abhinav dangeti <abhinav.dangeti@gmail.com>