syslog-lib.sh: Use lib to restart syslog service

Use restart_daemon() to restart syslog service.

Signed-off-by: Peng Haitao <penght@cn.fujitsu.com>
Reviewed-by: Jan Stancek <jstancek@redhat.com>
Reviewed-by: Wanlong Gao <gaowanlong@cn.fujitsu.com>
Tested-by: Jan Stancek <jstancek@redhat.com>