Fixed set creation in batch update index path results
Fixed set creation in batch update index path results

Summary:
3 variables were meant to be sets but were initialized as arrays, as discussed in #232. Corrected initialization to match definitions.

- [x] All tests pass. Demo project builds and runs.
- [x] I added tests, an experiment, or detailed why my change isn't tested.
- [x] I have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/.github/CONTRIBUTING.md)
Closes https://github.com/Instagram/IGListKit/pull/233

Differential Revision: D4213541

Pulled By: jessesquires

fbshipit-source-id: 5b2528d683bd6a2358fd8a1ff4e5fec58f4a59b1

zhubofei/IGListKit,Instagram/IGListKit,zhubofei/IGListKit,Instagram/IGListKit,Instagram/IGListKit,Sherlouk/IGListKit,charles0126dev/IGListKit,charles0126dev/IGListKit,zhubofei/IGListKit,charles0126dev/IGListKit,dshahidehpour/IGListKit,zhubofei/IGListKit,zhubofei/IGListKit,Instagram/IGListKit,dshahidehpour/IGListKit,Instagram/IGListKit,Sherlouk/IGListKit,Sherlouk/IGListKit,dshahidehpour/IGListKit