vfs_fruit: resource fork open request with flags=O_CREAT|O_RDONLY

vfs_fruit: resource fork open request with flags=O_CREAT|O_RDONLY

When receiving an SMB create request with read-only access mode and
open_if disposition, we end of calling the open() function with
flags=O_CREAT|O_RDONLY for the ._ AppleDouble file.

If the file doesn't exist, ie there's currently no rsrc stream, we create
it but then we fail to write the AppleDouble header into the file due to
the O_RDONLY open mode, leaving a 0 byte size ._ file.

Running this create requests against macOS SMB server yields an
interesting result: it returns NT_STATUS_OBJECT_NAME_NOT_FOUND even
though create dispotion is open_if. Another instance where the macOS SMB
server just exposes FSA behaviour (ie HFS+) and we have to adapt to be
compatible.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=12565

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>