vfs_fruit: return fake pipe fd in fruit_open_meta_netatalk()

vfs_fruit: return fake pipe fd in fruit_open_meta_netatalk()

Do not open the basefile, that conflict with "kernel oplocks = yes". We
just return a fake file fd based on dup'ing a pipe fd and ensure all VFS
functions that go through vfs_fruit and work on the metadata stream can
deal with it.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=12791

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Richard Sharpe <realrichardsharpe@gmail.com>
Reviewed-by: Volker Lendecke <vl@samba.org>