shadow-native: fix creation of home directories

shadow-native: fix creation of home directories

Pseudo was recently changed so that when system() calls are
made after a chroot(), the host binaries can no longer be found,
breaking the system("mkdir -p") approach when useradd creates
home directories.

Instead, use mkdir(2) to create home directories with a helper
function to ensure parent directories get created.

Signed-off-by: Scott Garman <scott.a.garman@intel.com>