ci: make server volume unique per build
Created by: jhchabran
It passed twice, with with 10 runs for both codeintelQA and backend integrations https://buildkite.com/sourcegraph/sourcegraph/builds/125255#1a078d31-63d1-479b-82e9-f7343163634c
Created by: jhchabran
It passed twice, with with 10 runs for both codeintelQA and backend integrations https://buildkite.com/sourcegraph/sourcegraph/builds/125255#1a078d31-63d1-479b-82e9-f7343163634c