Set "inet6 autoconf" individually on interfaces that have rtsol set in

hostname.if, previously netstart tried to configure them all at once
("ifconfig if0 if1 if2 inet6 autoconf").  From Delan Azabani, ok phessler@

src/etc/netstart

@@ -1,6 +1,6 @@
 #!/bin/sh -
 #
-#	$OpenBSD: netstart,v 1.153 2015/07/20 06:59:39 rpe Exp $
+#	$OpenBSD: netstart,v 1.154 2015/09/11 12:21:52 sthen Exp $
 
 # Turn off Strict Bourne shell mode.
 set +o sh
@@ -151,6 +151,21 @@ ifmstart() {
 	done
 }
 
+# IPv6 autoconf the interfaces in the list at $rtsolif
+# Usage: ifautoconf
+ifautoconf() {
+	printf 'IPv6 autoconf:'
+	# $ip6kernel will not have been set if we were invoked with a
+	# list of interface names
+	if ifconfig lo0 inet6 >/dev/null 2>&1; then
+		for curif in $rtsolif; do
+			printf ' %s' $curif
+			ifconfig $curif inet6 autoconf
+		done
+	fi
+	echo
+}
+
 # Get network related vars from rc.conf using the parsing routine from rc.subr.
 FUNCS_ONLY=1 . /etc/rc.d/rc.subr
 _rc_parse_conf
@@ -165,6 +180,7 @@ if [ $# -gt 0 ]; then
 		ifstart $1
 		shift
 	done
+	ifautoconf
 	return
 fi
 
@@ -246,10 +262,8 @@ ifmstart "" "trunk svlan vlan carp gif gre pfsync pppoe tun bridge pflow"
 # Configure all the carp interfaces which we know about before default route.
 ifmstart "trunk svlan vlan carp"
 
-if [ "$ip6kernel" = "YES" -a "x$rtsolif" != "x" ]; then
-	echo "IPv6 autoconf:$rtsolif"
-	ifconfig $rtsolif inet6 autoconf
-fi
+# Now that $rtsolif has been populated, IPv6 autoconf those interfaces
+ifautoconf
 
 # Look for default routes in /etc/mygate.
 [[ -z $dhcpif ]] && stripcom /etc/mygate | while read gw; do