Fix flaky test for ephemeral secrets

[peternose]

Fix flaky E2E test keymanager-ephemeral-secrets.

level=debug ts=2025-02-07T10:18:17.455589839Z caller=network.go:753 module=oasis/e2e/runtime/keymanager-ephemeral-secrets msg="node terminated" node=compute-1 err=null
level=debug module=libp2p caller=basic_host.go:382 ts=2025-02-07T10:18:20.741578223Z msg="failed to fetch local IPv6 address" module=libp2p:basichost error="no route found for ::"
Error: root: failed to run scenario: root: failed to run scenario: ephemeral key for epoch 3 should be available

[ptrus]

Also three very recent failures of the runitme-upgrade test:

level=error ts=2025-02-08T04:34:29.03251782Z caller=root.go:448 module=test-runner msg="failed to run scenario" err="root: failed to run scenario: compute-1: failed to query status: rpc error: code = DeadlineExceeded desc = latest balancer error: connection error: desc = \"transport: Error while dialing: dial unix /tmp/e2e/oasis-test-runner3835186094/compute-1-internal-1895000782.sock: connect: connection refused\"" scenario=e2e/runtime/runtime-upgrade run_id=0

• https://buildkite.com/oasisprotocol/oasis-core-ci/builds/14757#0194e3cb-1991-4fa2-a0a2-6820577367de
• https://buildkite.com/oasisprotocol/oasis-core-ci/builds/14741#0194df93-397a-4696-8645-5cb2ff53d96c
• https://buildkite.com/oasisprotocol/oasis-core-ci/builds/14735#0194dea4-c2c4-4e65-91f6-cdeca7c99f13