update time while network is connected

NTP update time from network while the network is not OK, so it should not
be excuted the network is disconnected to be for low power consumption

Test: as follows
    - built
    - flashed
    - booted
Change-Id: I17f2a9463551e254284ee8a9f894a95e983eee19
Signed-off-by: zhoulei <zhoulei5@xiaomi.com>