cli: fix nmcli timeout when disconnecting a device

$ nmcli dev disconnect nm-bond
Error: Timeout 10 sec expired.

When a software device is disconnected, it will be removed. And it may not go
to NM_DEVICE_STATE_DISCONNECTED state before that. So we need to listen to
"device-removed" signal.

Fixes:Beaker:test_log-NetworkManager_Test189_bond_activate