vfs_fruit: add manpage

Signed-off-by: Ralph Boehme <rb@sernet.de>
s4-torture: add testsuite for VFS modules

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

Signed-off-by: Ralph Boehme <rb@sernet.de>
wip: add test to selftest