The reason for this PR is many bug fixes in the nginx plugin for changes we haven't released yet are included in #5220 which may not make our next release. If it doesn't, we will (mostly) revert the nginx plugin back to its previous state to avoid releasing these bugs and will revert this PR after the release.
* Revert "Nginx IPv6 support (#5178)"
This reverts commit 68e37b03c8.
* Revert "Fix bug that stopped nginx from finding new server block for redirect (#5198)"
This reverts commit e2ab940ac0.
* Revert "Nginx creates a vhost block if no matching block is found (#5153)"
This reverts commit 95a7d45856.
* Allow authentication if there's no appropriate vhost
* Update test
* add flag to suppress raising error if no match is found
* Allow installation if there's no appropriate vhost
* remove traceback
* make new vhost ssl
* Fix existing bugs in nginxparser.py and obj.py
* Switch isinstance(x, str) to isinstance(x, six.string_types) in the Nginx plugin
* remove unused import
* remove unneeded custom copy from Addr
* Add docstring for create_new_vhost_from_default
* add test for create_new_vhost_from_default
* add configurator tests and leave finding the first server block for another PR
* don't assume order from a set
* address multiple default_server problem
* don't add vhosts twice
* update unit tests
* update docstring
* Add logger.info message for using default address in tlssni01 auth
