For short-lived commands the run pod can transition Running to Succeeded
between the running-pod check and the kubectl exec SPDY upgrade, leaving
the upgrade to fail with `container not found`. When stdout is not a TTY
(and DOKKU_FORCE_TTY is not set) the exec attach is only being used to
capture stdout, so stream the run pod logs in follow mode instead. The
pod's `TTLSecondsAfterFinished` of 60s keeps the kubelet's log file
readable for the duration of the call, eliminating the race.
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