Fix if there's a new connection of and exisiting device id, it will remove the exisiting device and the new one

[diogoViana95]

If you have one device connected and you try to connect another device with the same id, the existing device should disconnect itself but it also disconnects the new device.
The logs are the following:

{"level":"debug","listenAddress":"[::]:7000","listenNetwork":"tcp","msg":"accepted connection","remoteAddress":"127.0.0.1:32772","ts":"2019-10-22T16:12:58.0593416Z"} {"caller":"manager.go:144","level":"debug","msg":"device connect","ts":"2019-10-22T16:12:58.0593416Z","url":"/api/v2/device"} {"caller":"manager.go:169","id":"mac:000000000000","level":"debug","localAddress":"127.0.0.1:7000","msg":"websocket upgrade complete","ts":"2019-10-22T16:12:58.0623428Z"} {"caller":"handlers.go:227","id":"mac:000000000000","level":"debug","msg":"Connected device","ts":"2019-10-22T16:12:58.0693426Z"} {"caller":"manager.go:383","id":"mac:000000000000","level":"debug","msg":"explicit shutdown","ts":"2019-10-22T16:12:58.0703468Z"} {"caller":"manager.go:316","id":"mac:000000000000","level":"debug","msg":"writePump starting","ts":"2019-10-22T16:12:58.0703468Z"} {"caller":"manager.go:240","id":"mac:000000000000","level":"debug","msg":"readPump starting","ts":"2019-10-22T16:12:58.0703468Z"} {"caller":"manager.go:254","error":"read tcp 127.0.0.1:7000-\u003e127.0.0.1:32770: use of closed network connection","id":"mac:000000000000","level":"error","msg":"read error","ts":"2019-10-22T16:12:58.0713422Z"} {"caller":"manager.go:216","id":"mac:000000000000","level":"debug","msg":"pump close","ts":"2019-10-22T16:12:58.0713422Z"} {"caller":"manager.go:223","error":"close tcp 127.0.0.1:7000-\u003e127.0.0.1:32770: use of closed network connection","id":"mac:000000000000","level":"error","msg":"Error closing device connection","ts":"2019-10-22T16:12:58.0713422Z"} {"caller":"manager.go:385","id":"mac:000000000000","level":"debug","msg":"writePump exiting","ts":"2019-10-22T16:12:58.0713422Z"} {"caller":"manager.go:255","id":"mac:000000000000","level":"debug","msg":"readPump exiting","ts":"2019-10-22T16:12:58.0713422Z"} {"caller":"manager.go:383","id":"mac:000000000000","level":"debug","msg":"explicit shutdown","ts":"2019-10-22T16:12:58.0713422Z"} {"caller":"manager.go:216","id":"mac:000000000000","level":"debug","msg":"pump close","ts":"2019-10-22T16:12:58.0723412Z"} {"caller":"manager.go:223","error":"close tcp 127.0.0.1:7000-\u003e127.0.0.1:32772: use of closed network connection","id":"mac:000000000000","level":"error","msg":"Error closing device connection","ts":"2019-10-22T16:12:58.0723412Z"} {"caller":"manager.go:385","id":"mac:000000000000","level":"debug","msg":"writePump exiting","ts":"2019-10-22T16:12:58.0723412Z"} {"caller":"manager.go:254","error":"read tcp 127.0.0.1:7000-\u003e127.0.0.1:32772: use of closed network connection","id":"mac:000000000000","level":"error","msg":"read error","ts":"2019-10-22T16:12:58.0723412Z"} {"caller":"manager.go:255","id":"mac:000000000000","level":"debug","msg":"readPump exiting","ts":"2019-10-22T16:12:58.0723412Z"}

[joe94]

We're gonna verify this again.