s4/torture: fruit: remove use of localdir from test_adouble_conversion test

s4/torture: fruit: remove use of localdir from test_adouble_conversion test

The previous use of localdir and torture_setup_local_file() was
motivated by the fact that by default vfs_fruit rejects access to files
with a "._" prefix.

Since a previous commit allowed SMB access to ._ files, rewrite the
test_adouble_conversion() test to create the ._ AppleDouble file over
SMB.

This also renders torture_setup_local_file() obsolete.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=13155

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