[services] Tests - Use lazy static instead of functions

Summary:
Depends on D4413

Suggested in https://phab.comm.dev/D4325#124852
We can use Rust's lazy_static instead of functions to have static variables calculated in the runtime

Test Plan: services tests work as before

Reviewers: palys-swm, ashoat

Reviewed By: palys-swm, ashoat

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

Differential Revision: https://phab.comm.dev/D4425