convert string compare to use equality operators
convert string compare to use equality operators

Summary:
The changes in this diff changes string comparisons using the compare method to
using equality operators.

Motivation:
- readability, simplifies code
- compare method is intended for sorting functions

This is clang check used: [Link Here](https://clang.llvm.org/extra/clang-tidy/checks/readability-string-compare.html)

Reviewed By: yfeldblum

Differential Revision: D7675563

fbshipit-source-id: e25a9edc30dd61407ceb651793afce59c0d3543c

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