MB-12695: sanitize urls logged in xdcr checkpointing log messages

Change-Id: I2848ae5c674fe9359bbd8b5abc6a796ed3f8d7bf
Reviewed-on: http://review.couchbase.org/43342
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>