Test suite: newly added XMPP account is not persisted, and "Pidgin has the expected persistent accounts configured" doesn't notice

I see the second “Then Pidgin automatically enables my XMPP account” fail in “Scenario: Using a persistent Pidgin configuration”: I see the account manager, and the XMPP account we created before rebooting is not listed (what?!). OTOH, “Pidgin has the expected persistent accounts configured” has succeeded, so clearly something is wrong; and FWIW, I’ve verified that the random IRC nickname listed in the account manager is the same as during the previous boot. But the persistent accounts.xml does not contain the newly created account, so we have two bugs:

the new account is not persisted
“Pidgin has the expected persistent accounts configured” missed that, which hid the former bug

Feature Branch: test/11413-pidgin-persistence

Parent Task: #10288

Related issues

Related to #11306 (closed)

Original created by @intrigeri on 11413 (Redmine)

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