`libcrun_initialize_apparmor()` implementation could have more robust error handling

[eriksjolund]

This is of little importance.

When reading this code

crun/src/libcrun/utils.c

Lines 757 to 761 in df04868

	if (crun_dir_p_at (AT_FDCWD, "/sys/kernel/security/apparmor", true, err))
	{
	fd = open ("/sys/module/apparmor/parameters/enabled", O_RDONLY | O_CLOEXEC);
	if (fd == -1)
	return 0;

it seems an error would be leaked if both /sys/kernel/security/apparmor and /sys/module/apparmor/parameters/enabled do not exist, because crun_dir_p_at() would return -1 and open() would return -1.

(I haven't verified this by actually running the code, but I studied the crun_dir_p_at() implementation and the return value section
of the man pages of statx(), fstatat() and open())