service: some minor fix.

Signed-off-by: yangdongsheng <yangds.fnst@cn.fujitsu.com>
service_unittest: fix ignore_status unittest.

Signed-off-by: yangdongsheng <yangds.fnst@cn.fujitsu.com>
service: fix status parser .

status parser fix:
    * sys_v:
        Returns True if XXX is running.
        Returns False if XXX is stopped.
        Returns None if XXX is unrecognized.
    * systemd:
        Returns True if XXX.service is running.
        Returns False if XXX.service is stopped.
        Returns None if XXX.service is not loaded.

Signed-off-by: yangdongsheng <yangds.fnst@cn.fujitsu.com>