probe-multiplatform: when using psiphon as a circumvention method, URL list fetch doesn't work reliably

[hellais]

On build 5.0.0 (127) running on Android.

You choose in the test options for websites only one or two categories, then the websites manual run fails to execute with an error saying "Unable to download URL list. Please try again".

see screenshot

[hellais]

It seems like this is actually an issue with Psiphon and not related to the category code selection. I confirmed that it's not actually happening when Psiphon is turned off and it's happening even when all categories are on.

According to the logs it seems like we are failing to download URLs even before psiphon has completed the bootstrap:

2025-02-11 11:52:04 : INFO : Run Worker: start
2025-02-11 11:52:04 : DEBUG : ooniprobe-engine/v3.24.0  dirty= go1.22.2
2025-02-11 11:52:04 : DEBUG : starting 'psiphon' tunnel; please be patient...
2025-02-11 11:52:04 : WARN : Could not download urls
2025-02-11 11:52:04 : INFO : Run Worker: finished

This is indicative that this is more likely to be an engine issue rather than a mobile app issue. cc @DecFox

[hellais]

Reassigning this to @DecFox and moving it to the Engine board.