[CI] Add keyserver: yarn test to CI

Summary: NA

Test Plan: Will test via Buildkite CI

Reviewers: def-au1t, palys-swm, benschac, ashoat

Reviewed By: palys-swm, ashoat

Subscribers: ashoat, Adrian, yayabosh

Differential Revision: https://phabricator.ashoat.com/D4110