tests: improve coverage

missing tests

• each route should not work without custom header
• siteinfo => no tests
• current user => when anonymous
• binary => wrong eid and attribute types
• binary => no params sent
• login => try with invalid login, wrong login and password types
• rql/transaction => test permissions on get, set requests (create a new user without rights on some entities), test rollback works on earlier requests if a later one fails

Linked to cubicweb/cubicweb#861 (closed)