vfs_fruit: use check on global_fruit_config.nego_aapl for macOS specific behaviour

vfs_fruit: use check on global_fruit_config.nego_aapl for macOS specific behaviour

Ensure any non MS compliant protocol behaviour targetted at supporting
macOS clients are only effective if the client negotiated AAPL.

Currently this only guards the resource fork which only macOS client are
going to use, but subsequent commits add more this at this place.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=13646

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