shadow: fix building systemd with useradd-staticids.bbclass enabled
| groupadd: 'systemd-journal-gateway' is not a valid group name
Without useradd-staticids enabled, group 'systemd-journal-gateway' is created
by useradd and that seems not to care for GROUP_NAME_MAX_LENGTH which has 16 by
default.
Signed-off-by: Andreas Müller <schnitzeltony@googlemail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>