api.c: Fix string truncation warning

api.c: Fix string truncation warning

This commit fixes this warning in api.c:

api.c: In function ‘cgroup_read_value_begin’:
api.c:4114:47: warning: ‘snprintf’ output may be truncated before the
    last format character [-Wformat-truncation=]
    4114 |  snprintf(stat_file, sizeof(stat_file), "%s/%s", stat_path,
         |                                               ^
api.c:4114:2: note: ‘snprintf’ output 2 or more bytes (assuming 4097)
    into a destination of size 4096
    4114 |  snprintf(stat_file, sizeof(stat_file), "%s/%s", stat_path,
         |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    4115 |   name);
         |   ~~~~~

Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>