shadow-native: Add --root option in groupmems

shadow-native: Add --root option in groupmems

    Patch add_root_cmd_groupmems.patch that we apply to shadow-native
    allows program groupmems from the shadow utility package to chroot()
    so it can be used to modify etc/passwd and etc/group if they are
    located in a sysroot.

    The --root option in groupmems is needed for class useradd.

Signed-off-by: Mikhail Durnev <mikhail_durnev@mentor.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>