log vbucket compaction options

So that things like MB-11658 are more easily diagnosed.

Change-Id: I5f716e99fd4911eb53b053a598cad7fb04816cc6
Reviewed-on: http://review.couchbase.org/39179
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>