Handle case of 0 connect retries better for HTTP Spark Connections

[danielvdende]

resolves #131

Description

With a default of 0 connect_retries, confusing log messages show up. (see example below)

Running with dbt=0.18.1
Found 5 models, 12 tests, 0 snapshots, 0 analyses, 158 macros, 0 operations, 0 seed files, 3 sources

Warning: TEMPORARILY_UNAVAILABLE: Cluster <my-cluster-name> is temporarily unavailable. The current cluster state is Terminated. Please retry your request after 30 seconds.
        Retrying in 10 seconds (0 of 0)
Encountered an error:
Runtime Error
  Runtime Error
    TEMPORARILY_UNAVAILABLE: Cluster <my-cluster-name> is temporarily unavailable. The current cluster state is Terminated. Please retry your request after 30 seconds.

We encountered this while working with Databricks, where we had a cluster that had not been started yet.
The logs suggest that a retry is going to be carried out, but it isn't (because the retry count defaults to 0). Also, a sleep is carried out, even if no retries are to happen. This check prevents this from happening.

Checklist

• [ x ] I have signed the CLA
• [ x ] I have run this code in development and it appears to resolve the stated issue
• [ x ] This PR includes tests, or tests are not required/relevant for this PR
• [ x ] I have updated the CHANGELOG.md and added information about my change to the "dbt next" section.

[jtcohen6]

Thanks for the contribution @danielvdende! This change makes sense. Could you add a changelog entry, and add yourself to the list of contributors?

The failing test looks unrelated—seems to be an issue with executing a set statement through the new Databricks SQL endpoint.

[danielvdende]

Done @jtcohen6 ! Thanks for the swift response 👍