Fix tethering WTF issue

When enable/disable tethering quickly, tethering may have stopped
when Ipserver start creatFd().
As tethering iface is down due to tethering stopped, creatFd() will
throw ErrnoException: bind failed: ENODEV (No such device).
When tethering is stopped, this exception is normal, should not
rise WTF.

Bug: 233587050
Test: manual test
Change-Id: I2e200313d1bec2c1e1245e779f3875397127160d