inline system test fails intermittently

https://jenkins.isc.org/view/BIND/job/bind9-master-ubuntu1604-amd64/708/testReport/junit/bind/system/inline/

I:inline:check 'rndc signing -nsec3param' requests are queued for zones which are not loaded (49)
I:inline:failed

The failing check was only added recently (see #468 (closed)).