Merge lp://qastaging/~michael.nelson/launchpad/628711-generate-ppa-htacess-too-slow-try-2 into lp://qastaging/launchpad

Speed up the generate-ppa-htacess cron script.

= Summary =
This branch addresses bug 628711 - generate-ppa-htaccess is too slow.

== Proposed fix ==
Based on the discussion on the bug, this branch updates the script so that it:

1) Queries for *all* current subscriptions that should be marked as expired
and expires them,
2) Queries for all tokens that are now invalid (ie. based on subscriptions
that have been cancelled or expired) and deactivates them, noting the ppas
affected.
3) Finds all the ppas that have new tokens created since the last successful
run of the script, combines these with the ppas affected by token deactivation
and checks/recreates their htpasswd files.

== Pre-implementation notes ==
See bug 628711

== Implementation details ==

== Tests ==
bin/test -vvm test_generate_ppa_htaccess

== Demo and Q/A ==
I'll be starting the QA on dogfood now.

= Launchpad lint =

Checking for conflicts and issues in changed files.

Linting changed files:
  lib/lp/archivepublisher/scripts/generate_ppa_htaccess.py
  lib/lp/archivepublisher/tests/test_generate_ppa_htaccess.py