Close OffsetManager on init offsets (#1214)
Close OffsetManager on init offsets (#1214)

The OffsetManager wasn't closed after initializing the offsets
leading to go routing leaks.

Signed-off-by: Pierangelo Di Pilato <f5f1d2015efd0bb51da99f56609dc938930158a7@redhat.com>
knative-sandbox/eventing-kafka,knative-sandbox/eventing-kafka