Update git submodules

* Update diskimage-builder from branch 'master'
  - Unmount internal mounts on finalise errors
    
    This is only one line, but it takes a lot to untangle ...  basically
    the current "correct" path is:
    
    ---
     mk_build_dir()
      -> sets trap trap_cleanup EXIT
    
     ... stuff ..
    
     mount_proc_dev_sys
      -> mounts $TMP_MOUNT_PATH/<proc,dev.sysfs>
    
     pre-finalise.d
     finalise.d
    
     unmount_image $TMP_BUILD_DIR/mnt # nb == $TMP_MOUNT_PATH
      -> unmount_dir()
       -> recursive unmount everything inside TMP_MOUNT_PATH
    
     TMP_IMAGE_PATH=$(dib-block-device getval image-path)
     export TMP_IMAGE_PATH
    
     dib-block-device umount
     dib-block-device cleanup
    
     ... actually cleanup directories ...
    ---
    
    Our current failure exit trap does:
    
    ---
     dib-block-device umount
     unmount_image
     ...
    ---
    
    Note this is the *opposite* of what is done in the correct exit path.
    In the failure case, if a script fails in the finalise stages it leads
    to /proc, /sys, /dev etc. still being mounted inside the image; the
    "dib-block-device umount" call doesn't know anything about these
    mounts and tries to unmount the parent directory, and we get a hard
    failure with a busy mount, and all the mounts are subsequently leaked.
    
    Note that "unmount_dir", which is ultimately called by
    "unmount_image", already knows to skip those mounts that
    "dib-block-device umount" manages (this is the DIB_MOUNTPOINTS list).
    This is further evidence it should be called *before* the
    dib-block-device umount.
    
    Change-Id: Ibef3ce9d1167b9c4ff3d5717b113cd3ed374f5e3

diskimage-builder

@@ -1 +1 @@
-Subproject commit bdfc13a5c0d6d623d1303bf198591f5c84ae8233
+Subproject commit 528456407131c8771588fd3d53f91785b728752e