vfs_fruit: make use of adouble_open_from_base_fsp(ADOUBLE_RSRC) in fruit_open_rsrc_ad...

vfs_fruit: make use of adouble_open_from_base_fsp(ADOUBLE_RSRC) in fruit_open_rsrc_adouble()

The key is that we return a fake_fd to the caller and only open
the '._' file in the background.

The next vfs backend should only see the fsp from
adouble_open_from_base_fsp, while the vfs backends above
should only see the fake_fd.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
Autobuild-User(master): Ralph Böhme <slow@samba.org>
Autobuild-Date(master): Thu Jan 21 14:47:53 UTC 2021 on sn-devel-184