This fixes the issue with the "randomly changing" default

This fixes the issue with the "randomly changing" default
route. What it was is there are two places in ip_output.c
where we do a goto again. One place was fine, it
copies out the new address and then resets dst = ro->rt_dst;
But the other place does *not* do that, which means earlier
when we found the gateway, we have dst pointing there
aka dst = ro->rt_gateway is done.. then we do a
goto again.. bam now we clobber the default route.

The fix is just to move the again so we are always
doing dst = &ro->rt_dst; in the again loop.

PR:	 174749,157796
MFC after:	1 week