team: forbid incorrect fall-through in notifier

There are two breaks missing there. The result is that userspace
receives multiple messages which might be confusing.

Introduced-by: 3d249d4c "net: introduce ethernet teaming device"
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>