use mount --make-private on $FAI_ROOT/dev and $FAI_ROOT/dev/pts in …

…task updatebase to avoid "target is busy" errors and leftover /target and /target/dev mounts after simultaneous dirinstalls

lib/updatebase

@@ -10,8 +10,12 @@ echo "Updating base"
 if [ "$FAI_ACTION" = "install" -o "$FAI_ACTION" = "dirinstall" ]; then
     mount -t proc   proc   $FAI_ROOT/proc
     mount -t sysfs  sysfs  $FAI_ROOT/sys
-    [ -f /etc/init.d/udev ] && mount --bind /dev $FAI_ROOT/dev
+    if [ -f /etc/init.d/udev ]; then
+      mount --bind /dev $FAI_ROOT/dev
+      mount --make-private $FAI_ROOT/dev
+    fi
     mount -t devpts devpts $FAI_ROOT/dev/pts
+    mount --make-private $FAI_ROOT/dev/pts
 
     # if libc is upgraded init u is called in chroot environment and
     # then init will eat up much cpu time