Dli support not tested

[wasndas]

1. Check in isReachable() that self.dli.verify() gives the correct status.
2. Check that update() and switch() are working with a reachable and non reachable dli switch

[mmingyeong]

I checked. But when executing 'isReachable()' and 'update()' method, the error "Unexpected exception is <class 'TypeError'>: 'coroutine' object cannot be interpreted an integer". So I keep debugging 'powerswitch.py'