start: send state to legacy lxc-monitord state server even if no state clients registered

start: send state to legacy lxc-monitord state server even if no state clients registered

This pr https://github.com/lxc/lxc/pull/1618 kill lxc-monitord, for backwards compatibility,
we also send state to legacy lxc-monitord state server in function `lxc_set_state`.

we should also send state if there is no state clients registered, otherwise `lxc-monitor` client will
not get state change event if container changed state to `STARTING` or `RUNNING`.

Signed-off-by: 0x0916 <w@laoqinren.net>