Revert hotfix to #540 in beta, as it introduced issue #548. The fix to the...

Revert hotfix to #540 in beta, as it introduced issue #548.  The fix to the former does not address a regression.  The latter is a regression.

Revert "changelog note re issue #540"
Revert "upgrade mysql driver which fixes unhandled exception upon driver reconnect.  closes #540"

This reverts commit bf3d3ed3.
This reverts commit 844d7992.