net: Add missing braces to multi-statement if()s

One finds all kinds of crazy things with some shell pipelining.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>