[3.1.6 Backport] Reduce EOF logging from go-blip

Since the websocket library change (CBG-1901), EOF errors can be wrapped, resulting in info level EOF logging instead of debug. We want to keep these expected errors at debug to reduce the amount of log noise for expected behaviour.

This was missed in CBG-2495

Fix: https://github.com/couchbase/go-blip/pull/64