CBQE-1098: Declare buckets to avoid error

UnboundLocalError("local variable 'buckets' referenced before assignment",)"

Change-Id: I44112089378fcaec3a466781aa4af917291829aa
Reviewed-on: http://review.couchbase.org/25168
Reviewed-by: abhinav dangeti <abhinav.dangeti@gmail.com>
Tested-by: abhinav dangeti <abhinav.dangeti@gmail.com>