uclient-fetch: init_ca_cert: fix memory leak

uclient-fetch: init_ca_cert: fix memory leak

Fixes following memory leak:

 $ valgrind --quiet --leak-check=full uclient-fetch -q http://127.0.0.1:1922/does-not-exist

  51 (16 direct, 35 indirect) bytes in 1 blocks are definitely lost in loss record 4 of 9
   at 0x4C31A3F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
   by 0x4C33D84: realloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
   by 0x553C7DF: glob_in_dir (glob.c:1410)
   by 0x553D5E8: glob@@GLIBC_2.27 (glob.c:1097)
   by 0x401D62: init_ca_cert (uclient-fetch.c:503)
   by 0x401D62: main (uclient-fetch.c:741)

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