Increase log rotation threshold.

And decrease number of files accordingly.

Change-Id: I8954cf38535135352c65d3187504343b9294d3ac
Reviewed-on: http://review.couchbase.org/38712
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>