The checkds system test could fail if some parent secondary servers did
not yet loaded all the zones before ns9 started sending DS queries. This
leads to SERVFAIL responses, while the test case expects good DS
responses. In order to mitigate against this issue, call 'rndc loadkeys'
to quickly restart the checkds procedure again.
Also refactor the checkds system test, to get rid of the many zone
name duplications. Update the functions 'zone_check' and
'keystate_check' to make the zone name an FQDN so we can just pass
the 'zone' variable into the function.
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