Fix stale serviceaccount tokens

[michelesr]

Kubernetes version 1.21 graduated BoundServiceAccountTokenVolume feature
to beta and enabled it by default. This feature improves security of
service account tokens by requiring a one hour expiry time, over the
previous default of no expiration. This means that applications that do
not refetch service account tokens periodically will receive an HTTP 401
unauthorized error response on requests to Kubernetes API server with
expired tokens

kubernetes/enhancements#542

This commit forces kube-schedule-scaler to refresh token every minute,
and acts as workaround at least until pykube-ng implements automatic
token renewal.

[ruthwells]

refreshing every minute seems a lot for a token that lasts an hour, but if you already have a loop that runs every minute, and there are no adverse overheads from running this frequently it seems reasonable to use it.