kern/121706: "rtfree: 0xc4383870 has 1 refs" emitted repeatedly

[Bruce Cran]

The same change was made in net/route.c rev 1.120.2.3.
I don't know if all calls to rtfree(rt) should be converted to 
RTFREE_LOCKED(rt), but those remaining are in:

net/route.c:367
net/route.c:399
netinet/if_ether.c:808
netinet/if_ether.c:813
netinet/if_ether.c:831
netinet/if_ether.c:834
netinet6/in6_gif.c:373
netinet6/in6_gif.c:376
netinet6/in6_ifattach.c:768
netinet6/nd6_nbr.c:219

--
Bruce