Null-safe logging in Bootstrapper

If any exception occurred before logger initialization, catch block still tried to use logger and got NPE, which masked the real startup error.
Discussion in comments for https://github.com/neo4j/neo4j/pull/3450 is the showcase for such problem.
@lutovich can we then initialize `logging` properly? This code is already confusing enough as it is, adding more weirdness won't help in making it better.