[services] Tests - Read port from the env vars

Summary:
Depends on D4341

Raised in https://phab.comm.dev/D4252#121260

It is better to read the ports from the env vars and limit the number of places where we specify them to the minimum - ideally just one.

Test Plan: Services should work as usual.

Reviewers: palys-swm

Reviewed By: palys-swm

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

Differential Revision: https://phab.comm.dev/D4379