Add back the statschannel manykeys test case

Add back the statschannel manykeys test case

Add a test case that has more than four keys (the initial number of
key slots that are created for dnssec-sign statistics). We shouldn't
be expecting weird values.

This fixes some errors in the manykeys zone configuration (keys
were created for algorithm RSASHA256, but the policy expected RSASHA1,
and the zone was not allowing dynamic updates).

This also fixes an error in the calls to 'zones-json.pl': The perl
script excepts an index number where the zone can be found, rather
than the zone name.