[IPV4]: Fix secondary IP addresses after promotion

This patch fixes the problem with promoting aliases when:
a) a single primary and > 1 secondary addresses
b) multiple primary addresses each with at least one secondary address

Based on earlier efforts from Brian Pomerantz <bapper@piratehaven.org>,
Patrick McHardy <kaber@trash.net> and Thomas Graf <tgraf@suug.ch>

Signed-off-by: Jamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>