jshn: jshn_parse: fix leaks of memory pointed to by 'obj'

jshn: jshn_parse: fix leaks of memory pointed to by 'obj'

Fixes following leaks of memory:

 352 (72 direct, 280 indirect) bytes in 1 blocks are definitely lost in loss record 3 of 3
   at 0x4C31B25: calloc
   by 0x5042E1F: json_object_new_array
   by 0x5044B02: json_tokener_parse_ex
   by 0x5045316: json_tokener_parse_verbose
   by 0x504537D: json_tokener_parse
   by 0x401AA9: jshn_parse (jshn.c:179)
   by 0x401977: main (jshn.c:378)

 752 (72 direct, 680 indirect) bytes in 1 blocks are definitely lost in loss record 6 of 6
   at 0x4C31B25: calloc
   by 0x50424CF: json_object_new_object
   by 0x5044B38: json_tokener_parse_ex
   by 0x5045316: json_tokener_parse_verbose
   by 0x504537D: json_tokener_parse
   by 0x401AA9: jshn_parse (jshn.c:179)
   by 0x401977: main (jshn.c:380)

Signed-off-by: Petr Štetiar <ynezz@true.cz>