Bump server startup timeout in CI from 30s to 60s

Created by: chrismwendt

@kevin noticed CI was consistently failing for him on https://github.com/sourcegraph/sourcegraph/pull/5192

It looks like other PRs are also hitting the 30s timeout: https://buildkite.com/sourcegraph/sourcegraph/builds/41048#596d2110-90b6-43ea-942c-4221a022b633/77-109

And when the timeout is not exceeded, it usually takes ~20s

I'm recommending we bump the timeout to 1 minute now, and investigate what's taking so long in the future when the 1 minute timeout starts getting exceeded

See https://sourcegraph.slack.com/archives/C07KZF47K/p1565820787198000