update switch handling in vmd(8). vmd now gets switch information (rdomain,

etc) from underlying switch interface instead of handling this on its
own.
Diff from carlos cardenas, Thanks!
ok reyk@

src/etc/examples/vm.conf

@@ -1,4 +1,4 @@
-# $OpenBSD: vm.conf,v 1.7 2017/03/25 16:28:25 reyk Exp $
+# $OpenBSD: vm.conf,v 1.8 2017/11/11 02:50:07 mlarkin Exp $
 
 #
 # Macros
@@ -10,15 +10,14 @@ sets="/var/www/htdocs/pub/OpenBSD/snapshots/amd64/"
 #
 
 switch "uplink" {
-	# This interface will default to bridge0, but switch(4) is supported
+	# This switch will use bridge0, defined by /etc/hostname.bridge0, as
+	# the underlying interface.  switch(4) is also supported
 	#interface switch0
-
-	# Add additional members
-	add em0
+	interface bridge0
 }
 
 switch "local" {
-	add vether0
+	interface bridge1
 	down
 }