Validate --electrs-connect Param

[adamkrellenstein]

Right now if you just pass the IP address e.g., you get a mysterious error:

 ~/ curl 'https://dev.counterparty.io:4000/v2/addresses/bc1q0eapk4tyqa7r2vcta6z6v2mgnqcux3kfkmurzp/compose/mpma?verbose=true&destinations=1GcwGwfCaTbRQ3ahju6GEiqwrbBACkBAPG%2Cbc1q4d2uqawh6tnlrkuy83hvjagk39em38m3ly7wrh%2C1KMByG7bhzKFmw2fYK4UQm5QnjdxDyTSLr&assets=A11034450232500713599%2CA359378403273191364%2CA16122126641873698406&quantities=11%2C550000000%2C10&allow_unconfirmed_inputs=true&exact_fee=1&inputs_set=0d54edc04542b3591b3f938e8e2ba402f026feb20161c6b042d81ad22a69acf1%3A0%2Ccba5822f350cdf6236dd59787fa178643697c33d7de6d15291c2a5c64c0cafcd%3A0%2Cc352136ec81bcd0b6e2875caeca1b83a6bb9411b03c391d3a2c840f4234bbf82%3A15%2C4b57b96798485cd45b9db103dd01857e82582bf72b2a4b1e682ad4f462ca5f7e%3A0&exclude_utxos_with_balances=true&disable_utxo_locks=true' | jq
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   143  100   143    0     0    342      0 --:--:-- --:--:-- --:--:--   342
{
  "error": "Electrs error: No connection adapters were found for 'electrs-service:3000/address/bc1q0eapk4tyqa7r2vcta6z6v2mgnqcux3kfkmurzp/txs'"
}

It's also not an "electrs error".

Also should this be --electrs-connect and not --electrs-url??