client-test: add ACL tests

- grant and revoke permissions as volume owner
- copy and list files with a single permission ('write' or 'read')
- try to copy files without 'write' permission
- try to change permissions as normal user and non-owner
client-test: various improvements and cosmetics

- improve deleting of remote files
- add a function to create files with different blocksizes
- reorganize error messages
- fix handling of profiles