Handle error during connection in sleep mode.

[ngraziano]

If TV is in sleep mode (not totally off) when I try to connect, its response is :

{"error":[7,"not power-on"],"id":1}

and there is not the necessary cookie for authentication but is_connected() return True

I get sleep mode for few minutes when I turn the TV off.

[ngraziano]

I change to use response.json(), it was use before for log so this should be good. I also change the test to be allow null response.

[antonioparraga]

perfect!