Included configurations in nsd.conf.d tend to depend on each other. For
example when referring a TSIG key from 80-generates-keys in
90-generated-zones, running nsd-checkconf on these individual files
would cause an error.
It is sufficient and better to just check the main nsd.conf file, as it
combines all included configurations in the check.
Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>