Rows parameter is not honored during import in some cases

1. The rows parameter is not honored in non-debug mode.
2. During debug mode, the rows parameter for a new request resets the old value. Therefore, the import will abort immediately, if rows is not specified on a subsequent request and if the original value for rows was greater than the default (10).

The first one is an enhancement and the second is a major bug. The fix for both is very related and it is best to handle both in the same issue.