[IPV6]: Fix source address selection.

The commit 95c385 broke proper source address selection for cases in which 
there is a address which is makred 'deprecated'. The commit mistakenly 
changed ifa->flags to ifa_result->flags (probably copy/paste error from a 
few lines above) in the 'Rule 3' address selection code.

The patch restores the previous RFC-compliant behavior.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>