wic: Fix permissions when using exclude or include path

When parameters include_path or exclude_path are passed to the rootfs
plugin, it will copy the partition content into a folder and make all
the modifications there.

This is done using copyhardlinktree(), which does not take into
consideration the content of the pseudo folder, which contains the
information about the right permissions and ownership of the folders.

This results in a rootfs owned by the user that is running the wic
command (usually UID 1000), which makes some rootfs unbootable.

This bug can be easily triggerd with the following .wks

part / --source rootfs --fstype=ext4 --exclude-path=home

And this sequence:

$ wic create test-permissions -e core-image-minimal -o test/
$ sudo mount test/test-permissions-202004080823-sda.direct.p1 /mnt
$ ls -la /mnt/etc/shadow

To fix this we copy the content of the pseudo folders to the new folder
and modify the pseudo database using the "pseudo -B" command.

If the rootfs is not a rootfs generated by bitbake a warning is shown
making the user aware that the permissions on the target might not match
what he expects.

WARNING: /tmp/test/../pseudo folder does not exist. Usernames and permissions will be invalid

Cc: Paul Barker <pbarker@konsulko.com>
Signed-off-by: Ricardo Ribalda Delgado <ricardo@ribalda.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit fd739c15)
Signed-off-by: Steve Sakoman <steve@sakoman.com>