Fix database retry connection issues

Backport of the ["NoMethodError: undefined method `error_field' for nil:NilClass"](https://github.com/rails/rails/commit/be913c3964069fa9ff7c8a615e06705e3a6ec435) that fixes:
https://bugzilla.redhat.com/show_bug.cgi?id=1127789

Added a new PGError retryable connection message "connection not open" to fix:
https://bugzilla.redhat.com/show_bug.cgi?id=1120364

Both errors were recreated somewhat reliably by:
1. starting a rails console 
2. 100.times { User.first; sleep 0.1 }  # SomeModel.first
3. Then, restarting postgresql in another session.