Fix JSON report zones output

Fix JSON report zones output

Previously multiple JSON objects would be in the output of
zns-report-zones if there were more than 1024 zones requested because of
the chunked requests sent by nvme-cli.

Fix this to output a single JSON object with one zone_list. This is done
by passing around and appending to the zone_list, then outputting all of
it once after receiving all the reports.

Signed-off-by: Brandon Paupore <brandon.paupore@wdc.com>