Plug a mem leak in g-file-info test

Plug a mem leak in g-file-info test

==2395== 64 bytes in 1 blocks are definitely lost in loss record 381 of 407
==2395==    at 0x4005BDC: malloc (vg_replace_malloc.c:195)
==2395==    by 0x4005C66: realloc (vg_replace_malloc.c:476)
==2395==    by 0x40571A5: g_realloc (gmem.c:181)
==2395==    by 0x401D670: g_ptr_array_maybe_expand (garray.c:968)
==2395==    by 0x401DD0B: g_ptr_array_add (garray.c:1225)
==2395==    by 0x4199AA9: g_file_info_list_attributes (gfileinfo.c:646)
==2395==    by 0x80491CE: test_g_file_info (g-file-info.c:76)

==2395== 132 (64 direct, 68 indirect) bytes in 1 blocks are definitely lost in loss record 396 of 407
==2395==    at 0x4005BDC: malloc (vg_replace_malloc.c:195)
==2395==    by 0x4005C66: realloc (vg_replace_malloc.c:476)
==2395==    by 0x40571A5: g_realloc (gmem.c:181)
==2395==    by 0x401D670: g_ptr_array_maybe_expand (garray.c:968)
==2395==    by 0x401DD0B: g_ptr_array_add (garray.c:1225)
==2395==    by 0x4199A82: g_file_info_list_attributes (gfileinfo.c:642)
==2395==    by 0x80492B7: test_g_file_info (g-file-info.c:86)

Bug #628331.