Fix unexpected additional resolved urls in testIconDownloader

[AMurkin]

I got unexpected additional resolved urls in testIconDownloader. Actual numbers were greater than expected for some test cases.
Set Config::Security_IconDownloadFallback to false before the test.

Testing strategy

It gave me:

> ./build/tests/testicondownloader
...
Totals: 23 passed, 0 failed, 0 skipped, 0 blacklisted

Type of change

• ✅ Bug fix (non-breaking change that fixes an issue)

[droidmonkey]

This has never been a problem before

[AMurkin]

I thought so. I'm certain this happens because I have keepassxc installed and their configuration affects tests. So it needs to have local configuration initialized somewhere in tests (but I don't know where). This been said, I still think my changes are useful.

[droidmonkey]

A new config file is made for each test, do you have an environment variable set directing where the config file is?

[AMurkin]

No, I don't have environment variables related to keepass.
QFileInfo(config()->getFileName()).absolutePath() gives me ~/.config/keepassxc in TestIconDownloader::testIconDownloader().