Wire up retry count config to NVD provider

[wagoodman]

This PR primarily wires up a new request_retry_count option to NVD with a default of 10 (a rather high number since the API tends to show issues). This also adjusts the jitter and display behavior of the http.get helper:

• now the sleep interval (and not the backoff) is shown when in the "attempting in X seconds" log message
• jitter applies to the first sleep interval (not the second)

[wagoodman]

Bypassed checks since NVD API is in a degraded state