[Services] Avoid using GTest in docker

Summary:
The test suites for services require gtest, however, it's not
currently available in our docker workflow.

This is in preparation of other changes which will use BUILD_TESTING to
determine if the test suite should be built.

Test Plan: Services CI gates pass

Reviewers: max, atul, abosh, varun, karol, tomek

Reviewed By: atul

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D5121