HTTPCreds: remove all cookies when logging out

[ogoffart]

Some custom server use persistent cookies with the auth token. So we should
clear all the cookies when disconnecting.
Account::clearCookieJar is only called from the HTTPCredentials. This funciton
is not used for shibboleth.
There is probably no reasons to keep the HTTP cookie anyway.

Issue #5370

[mention-bot]

@ogoffart, thanks for your PR! By analyzing the history of the files in this pull request, we identified @jturcotte, @danimo and @ckamm to be potential reviewers.

[SamuAlfageme]

HTTP basic auth. working like a charm now. Have to try a couple more scenarios, but seems to be all right.

Once it's done, should we cherrypick this into https://github.com/owncloud/client/releases/tag/v2.2.4 ?.

cc/ @michaelstingl

[SamuAlfageme]

Leaving here a corner case due to the same account being able to log in multiple times in the same client (#5305)

Actual behavior:

Both cookies are wiped as they refer to the same username@domain combination.

Expected behavior:

The cookies could be wiped based on which was logged out and which wasn't

Steps to reproduce:

1. Log in to the same account with the same sync client
2. Log out of one of the accounts - the other account is fully usable
3. Close the client and reopen
4. Both accounts ask for password.
5. Enter one of the passwords, leave the other logged out.
6. Repeat 3.
7. Both accounts are logged in.

As said, this is a corner case, don't know how relevant.

[michaelstingl]

@SamuAlfageme From my perspective, same account logged in multiple times, should be out of scope. (but there are other opinions)

[SamuAlfageme]

@owncloud/desktop-developers this is ready to be merged & cherrypicked to v2.2.4 tag, anyone?

[guruz]

@SamuAlfageme 2.2.4 is already released and tags can't be changed. Was there a decision to do a 2.2.5 for this?

[michaelstingl]

@guruz I need a patch that would work on the 2.2.4 tag. No 2.2.5 required.

[guruz]

@michaelstingl https://gist.github.com/guruz/f81cbc4cbcc499f9a87ee74f1fc9e86b (haven't tested it on 2.2.4 though but it should work)

[michaelstingl]

@SamuAlfageme Could you test-drive https://gist.github.com/guruz/f81cbc4cbcc499f9a87ee74f1fc9e86b and give a 👍 if it could be applied to 2.2.x?

[SamuAlfageme]

After struggling a bit because of some unrelated issues to test the patch over 2.2.4, finally did in both Win7 and OS X, and it's working as expected 🎉

Couple of concerns though:

1. If we don't make a specific tag containing the patch, building a client with it it's going to be hard from ownbrander.
2. If someone uses a v2.2.4 client with the patch applied, the update notification is triggered; even if the patched version is built on top of 2.2.4, updater will try to install the stable:

cc/ @michaelstingl