nvme-cli: JSON format Memory leak fixes.

[Chaitanya Kulkarni]

Hi,

Following patch series provides multiple memory leak fixes
for nvme-cli commands. Memory leaks were found especially
when using JSON format for following list of commands:-
 1. id-ctrl.
 2. id-ns.
 3. error-log.
 4. resv-report.
 5. smart-log.
 6. fw-log.
 7. json_add_smart_log().

Regards,
-Chaitanya