CBSE-1444: add formatted internal_settings to /diag output

So that folks don't need to inspect config dump manually to see if
anything was changed or not.

Change-Id: Ic1e59df4510aa372d0bdda39b38be2d029344148
Reviewed-on: http://review.couchbase.org/42208
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>