[beta blocker blocker] Test updating for poll.module

And here's an initial patch. I'm sure it will fail, but sadly that's because of genuine bugs in the upgrade path.

Summary of the currently failing tests:

Message	Group	Filename	Line	Function	Status
Undefined variable: field	Notice	taxonomy.install	410	taxonomy_update_7005()
Undefined index: poll	Notice	node.install	549	node_update_7006()
Undefined index: poll	Notice	node.install	549	node_update_7006()
Undefined index: poll	Notice	node.install	549	node_update_7006()
Undefined index: poll	Notice	node.install	549	node_update_7006()
Undefined index: poll	Notice	node.install	549	node_update_7006()
Undefined index: poll	Notice	node.install	549	node_update_7006()
Undefined index: poll	Notice	node.install	549	node_update_7006()
Undefined index: poll	Notice	node.install	549	node_update_7006()
Undefined index: poll	Notice	node.install	549	node_update_7006()
Undefined index: poll	Notice	node.install	549	node_update_7006()
Attempt to create an instance of field comment_body on bundle comment_node_poll that already has an instance of that field.	FieldException	field.crud.inc	674	field_create_instance()
HTTP response expected 200, actual 500	Browser	upgrade.test	231	UpgradePathTestCase->performUpgrade()
The upgrade was completed successfully.	Other	poll.test	32	PollUpgradePathTestCase->testPollUpgrade()

The first exception (undefined variable field) is being resolved at #706842: Improve comments for the taxonomy upgrade path. The last two failures are caused by the preceding FieldException.
The field_create_instance function is probably called from node_update_7006 indirectly, so all other exceptions seem related; Looking into that.

Updated version of the tests. Using drupal_install_modules doesn't rebuild {node_types} causing various warnings and errors noted above. New solution is to enable the modules manually before running the content generation script.

Another strange issue is that the test only works when the poll.module is actually enabled on the site running the test. Otherwise (for a reason unknown to me) the "Results" tab isn't displayed on poll nodes, only "View" and "Edit".

Expecting one failure now ("undefined variable: field").

There are more tests failing. Strange thing is, it doesn't happen when poll.module is enabled on the site running the tests.

First debugging yields the following results:
- module_list includes poll.module
- module_implements('menu') doesn't return poll.module, causing the poll menu items not being included in {menu_router}.

Further investigation needs to point out why this happens.

Lets see what this gives on the testbot...

Major thanks to chx for helping and guiding me to find why these apparently strange things were happening.

Leave module_list(TRUE) in performUpgrade, so the tests know about newly enabled/disabled modules.

#7: 848368-poll-test-3.patch queued for re-testing.

#9: 848368-poll-test-4.patch queued for re-testing.

Another try, now we explicitly load modules that are enabled in the test database, but not on the testing client.

Needs review again

#14: 848368-load-new-modules.patch queued for re-testing.

Not there yet. Testbot complains about an error in locale.test now, but not sure how that can be related...

RTBC based on #17 and my review of Damien's modifications

This patch makes some changes to the upgrade testing framework as well as add a more generic testing database, both of which are needed for #706842: Improve comments for the taxonomy upgrade path, so marking it accordingly.

Made some corrections to the generation script, which now also enables needed modules and runs cron after installing modules (but before adding the content).
Modifies the dump script to include a header containing the loaded modules as well.