Don't hide the reason why config synchronization failed.

Change-Id: I1731735d3b55ddcdb189bc6dc03cfd66f2dbfe90
Reviewed-on: http://review.couchbase.org/36028
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>