sysklogd: lower the ALTERNATIVE_PRIORITY in case of systemd

sysklogd: lower the ALTERNATIVE_PRIORITY in case of systemd

The sysklogd package hasn't got systemd support yet. So in case of
a systemd based system, the commands and corresponding configuration
files should have a lower priority than that of the busybox's syslogd
and klogd utilities. These two utilities from busybox have internal
systemd support if CONFIG_FEATURE_SYSTEMD is enabled. And that config
item is enabled by default.

[YOCTO #5066]

(From OE-Core rev: 45d18a1b6bcdc56d252b289d0d304b26799943b0)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>