CBIDXT-109: Avoid magic numbers.

magic numbers are converted to configuration parameters.

Change-Id: I0af2e6c52b5ca8dc91b1ca65833f794ee6a230b8
Reviewed-on: http://review.couchbase.org/42457
Reviewed-by: John Liang <johliang00@gmail.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>