MB-12210: log remote_clusters_info activity to xdcr logs

Change-Id: Ie2a313867114c6685c78fc9d618f3601e35bccea
Reviewed-on: http://review.couchbase.org/42531
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>