add gitserver startup probe (#249)

This adds a startup probe to gitserver so that it's not immediately
killed while it's starting up and migrating the on-disk format for
repos.

Author: camdencheek

base/sourcegraph/gitserver/gitserver.StatefulSet.yaml

@@ -37,6 +37,14 @@ spec:
               value: http://$(OTEL_AGENT_HOST):4317
           image: index.docker.io/sourcegraph/gitserver:6.0.0@sha256:aec9bf6993c243a283109104cd7c44be3c85680b77e3e8be0c5fba8f01a3bd35
           terminationMessagePolicy: FallbackToLogsOnError
+          # Temporary: when migrating from repo names to repo IDs on disk,
+          # gitserver can take a little while to start up. To avoid killing the
+          # pod because of a failed liveness probe, we give it 2 minutes to start up.
+          startupProbe:
+            tcpSocket:
+              port: rpc
+            failureThreshold: 120
+            periodSeconds: 1
           livenessProbe:
             initialDelaySeconds: 5
             tcpSocket: