Add in wait for pods to be initiated
Created by: davejrt
Adds in a small delay for pods to be created (not ready) by the kubelet. I saw in local testing that some pods were very slightly behind the rest. Given how quickly this script runs through commands it's possible the pod hasn't been created before we check that it's ready.
fixes https://github.com/sourcegraph/sourcegraph/issues/32403
Test plan
Green build on main-dry-run https://buildkite.com/sourcegraph/sourcegraph/builds/138656#bc3329ff-daf6-4616-a44a-fa670cff5afa/1