[#724] Fix incorrect Mongoid import strategy
[#724] Fix incorrect Mongoid import strategy

* For collections less then :per_page, no data would be imported.
* For a collection of 1,200 items, the last 200 documents won't be imported for the default batch of 1,000

Fixes #724

Cc: da39a3ee5e6b4b0d3255bfef95601890afd80709@tobycox

fabn/retire,tklee/tire_shiphawk,dbose/retire,brijeshgpt7/retire,1776/tire,karmi/retire,HenleyChiu/tire,ChapterMedia/tire,iamrahulroy/retire,elbuo8/retire,Telmate/tire,doximity/tire,mavenlink/retire,rubydubee/retire,zaharpecherin/retire