Log level for Exporter failures

Is your feature request related to a problem? Please describe.
Currently, a log warning is produced when any failure during span export occurs.

In looking at the JaegerGrpcSpanExporter in particular, I was curious how it's possible to know whether a failure to export is a transient failure vs a more serious problem, such as an endpoint that can not be connected to because the URI is wrong, even if it's a valid URI.

Describe the solution you'd like
In the situation of an endpoint that can't be connected to, maybe it's possible to track such a connection issue and log an error instead of a warning if that same error occurs a certain number of times, and then stop logging if the failure continues.

I appreciate it needs to handle transient failures and log those at a warning level, but for a persistent failure, something more than a log warning would be preferred.

The issue names JaegerGrpcSpanExporter but no file or test. Start there and trace the current warning path, then clarify how transient and persistent connection failures should be distinguished. Done means the logging behavior, escalation threshold, and suppression of continued failures are defined and covered by tests.