[4.4] Fix exception handling in `Session.close()`

[robsdedude]

Exceptions raised during some cleanup steps in session.close could have left the session in an unclean state. In particular, the session wouldn't be marked as closed. Moreover, errors encountered when consuming outstanding auto-commit results during session closure were silently swallowed.

Back port of https://github.com/neo4j/neo4j-python-driver/pull/800