[NETFILTER]: Cleanup find_appropriate_src() Fix

The fix to find_appropriate_src left a stupid test, which has no
effect but is incoherent at best.  It covers a corner case: if a
previous connection from this source was mapped onto a different IP
address (because it was explicitly told to), should the next one be
mapped that was as well, if no explicit rule says to remap the src IP?

I think the answer is yes: unless the user explicitly tells us to map
into a particular range, we should follow the Kegel draft.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/netfilter/ip_nat_core.c

@@ -128,16 +128,13 @@ in_range(const struct ip_conntrack_tuple *tuple,
 	unsigned int i;
 
 	for (i = 0; i < mr->rangesize; i++) {
-		/* If we are allowed to map IPs, then we must be in the
-		   range specified, otherwise we must be unchanged. */
+		/* If we are supposed to map IPs, then we must be in the
+		   range specified. */
 		if (mr->range[i].flags & IP_NAT_RANGE_MAP_IPS) {
 			if (ntohl(tuple->src.ip) < ntohl(mr->range[i].min_ip)
 			    || (ntohl(tuple->src.ip)
 				> ntohl(mr->range[i].max_ip)))
 				continue;
-		} else {
-			if (tuple->src.ip != tuple->src.ip)
-				continue;
 		}
 
 		if (!(mr->range[i].flags & IP_NAT_RANGE_PROTO_SPECIFIED)