Connection failure logging is too aggressive

[mediocretes]

Looking at https://github.com/Instrumental/instrumental_agent-java/blob/master/src/main/java/com/instrumentalapp/Connection.java#L276

It looks like it will log a connection failure under 'severe' even if there are lots of retries left. This should be debug or warn at most, until the last one.

[janxious]

Concur