[services] Fix reactor status holder

Summary: I noticed that there are still ReactorUtility files and since we agreed on the name ReactorStatusHolder, it should also be applied everywhere in the code as well as in the files' names.

Test Plan:
Services should build normally

cd services
yarn test-blob-service-dev-mode
yarn test-backup-service-dev-mode

Reviewers: palys-swm, ashoat

Reviewed By: ashoat

Subscribers: ashoat, palys-swm, Adrian, atul, yayabosh

Differential Revision: https://phabricator.ashoat.com/D4002