s4:torture: add boilerplate code for testing specific VFS modules

Signed-off-by: Ralph Boehme <rb@sernet.de>
s4:torture: add wrapper functions

Add wrapper functions that connect two trees with sharenames taken
from passed option.

Signed-off-by: Ralph Boehme <rb@sernet.de>
s4:torture: add boilerplate code for vfs_fruit

Signed-off-by: Ralph Boehme <rb@sernet.de>
s4:torture:vfs_fruit: add test reading Netatalk metadata

Signed-off-by: Ralph Boehme <rb@sernet.de>