Fix bit rot when deleting addresses in addvpubaddr.

It assumed addresses were unused if node_id was NULL.  This used to be
true before the introduction of per-experiment dynamic address pools (when
public addresses were mapped one-to-one with VMs).  Unfortunately this
code was not updated when experiment address pools were added, and so
it would have permitted the deletion of currently assigned addresses.

utils/addvpubaddr.in

@@ -92,7 +92,8 @@ for( $i = $first; $i <= $last; $i++ ) {
 
     if( $delete ) {
 	$result = DBQueryWarn( "DELETE FROM virt_node_public_addr WHERE " .
-			       "IP='$addr' AND node_id IS NULL" );
+			       "IP='$addr' AND node_id IS NULL AND " .
+			       "pid IS NULL AND eid IS NULL" );
     } else {
 	$result = DBQueryWarn( "INSERT INTO virt_node_public_addr SET " .
 			       "IP='$addr', mask='$netmask'" );