Cron `reloadValidators` should rely on `upcheck` instead of `healtcheck` endpoint to start

[pablomendezroyo]

At the beggining of the critical cron reloadValidators, it checks if the healtcheck endpoint returns any error, this check should not be done since it does not mean that the reloadValidators would fail. Instead it should check whenever the web3signer is up or not calling the upcheck endpoint.

See upstream docs