vfs_xattr_tdb: don't leak the fd into the caller

vfs_xattr_tdb: don't leak the fd into the caller

This is subtle: generally fsp_set_fd(fd) is called in the caller of
SMB_VFS_OPENAT() in non_widelink_open().

fsp_set_fd() has a check that asserts certain combindations of the existing
fsp->fh->fd and the new fd. Both being valid fds is not allowed.

Therefor inside the VFS we must reset fsp->fh->fd if we've set it.

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