bug: uuid mismatch on bootstrap leader

When bootstrapping an instance, there're two possible execution paths - start_boot and start_join. While start_join takes all uuids from JoinResponse, start_boot already deals with a bootstrapped box.cfg (it's done in start_discover, refer to [1]). In order to make uuids consistent across box.cfg and topology module, start_boot stage is preceded with rebootstrap.

This case is also covered with a pytest.

• [1] doc/clustering.md

Close: #69 (closed)