vfs_fruit: fix fruit_check_access()

vfs_fruit: fix fruit_check_access()

Applying fcntl read locks requires an fd opened for reading. This means
we have to check the open flags of an fd and if the fd is not opened for
reading, we can't use it to set shared fctnl locks.

Iow we won't be applying interop locks with Netatalk for files openend
write-only.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=12427

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Uri Simchoni <uri@samba.org>