[services] consistently return when trying to remove non-existent item

Summary:
Depends on D3990

Raised in https://phabricator.ashoat.com/D3990#112037

We should be consistent and throw if someone tries to remove an item that does not exist. That clearly means the logic's invalid.

Test Plan:

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

Reviewers: geekbrother, palys-swm

Reviewed By: geekbrother, palys-swm

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

Differential Revision: https://phabricator.ashoat.com/D3999