s4:torture: test setting EOF of a stream to 0 with enabled AAPL extensions

s4:torture: test setting EOF of a stream to 0 with enabled AAPL extensions

macOS SMB server uses xattrs as storage backend for streams, directly
exposing xattr get/set characteristics. Setting EOF on a stream to 0
just deletes the xattr as macOS doesn't support 0-byte sized xattrs.

Note that this does not apply to the AFP_AfpInfo and AFP_Resource
streams, they have even stranger semantics and we have other tests
for those.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=13441

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