[Checkins] [zopefoundation/ZODB] 1b9475: Review Connection/DB closure

[GitHub]

  Branch: refs/heads/closure
  Home:   https://github.com/zopefoundation/ZODB
  Commit: 1b9475d413705e510ff2f19ee6449688ffb04d46
      https://github.com/zopefoundation/ZODB/commit/1b9475d413705e510ff2f19ee6449688ffb04d46
  Author: Julien Muchembled <jm at nexedi.com>
  Date:   2017-11-08 (Wed, 08 Nov 2017)

  Changed paths:
    M src/ZODB/Connection.py
    M src/ZODB/DB.py

  Log Message:
  -----------
  Review Connection/DB closure

In addition to some micro-optimisation, this fixes the following minor issues:
- Closing a DB left Connections registered to the global transaction manager.
  Which broke at least multi-db because only such primary connections were
  ignored with monkey-patches.
- Stop calling the real newTransaction when aborting an existing transaction.
  This was not the case if explicit_transactions=0.