[ale] Remove unnecessary log files when sink starts.

Namely the ones that have sequence number larger than what we expect
with current rotation settings.

Change-Id: I38d158c41238e70b995bb5e0fb669bf3fc2c7a43
Reviewed-on: http://review.couchbase.org/37942
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>