s4:torture/vfs/fruit: ensure test_adouble_conversion() uses a non-emtpy resourcefork

s4:torture/vfs/fruit: ensure test_adouble_conversion() uses a non-emtpy resourcefork

This ensures the resource fork is not deleted as part of the AppleDouble file
conversion for the option fruit:wipe_intentionally_left_blank_rfork=yes.

This is currently not a problem in selftest, as we don't enable the option, but
a subsequent commit will run all vfs.fruit tests against a share with this
option enabled.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=13958

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