always unmount /proc after chroot - fixes building of CD

cbox-tree.d/usr/lib/cryptobox/chroot-start.sh

@@ -26,7 +26,7 @@ mount -n --bind "$TMP_DIR" "$MNT_DST"
 [ ! -e /dev/urandom ] && mknod "/dev/urandom" c 1 9 && chmod 444 "/dev/urandom"
 [ ! -e /dev/console ] && mknod "/dev/console" c 1 5 && chmod 660 "/dev/console"
 
-[ ! -e /proc/mounts ] && mount -n -t proc proc /proc
+mount -n -t proc proc /proc
 
 # default language setting - prevents dpkg error messages
 export LANG=C
@@ -41,6 +41,5 @@ if [ $# -gt 0 ]
   fi
 
 umount -n "$MNT_DST"
-# check for an active chroot environment
-[ -z "$(ps -e | grep chroot-start.sh)" ] && umount -n proc
+umount -n proc || true
 rm -r "$TMP_DIR"