[stable33] getById: don't setup for all users with access by default

[icewind1991]

Partly reverts the behavior of #57913 to use the already-setup mounts.

Only when no already setup mounts are found, do we perform extra setups, and then only for the relevant user (if a user is available)

Extracted from #57910

[nickvergessen]

 
1) Test\Files\ViewTest::testGetPathNotExisting
Failed asserting that exception of type "Error" matches expected exception "OCP\Files\NotFoundException". Message was: "Call to a member function getUID() on null" at
/home/runner/actions-runner/_work/server/server/lib/private/Files/Node/Root.php:448
/home/runner/actions-runner/_work/server/server/lib/private/Files/Node/Root.php:393
/home/runner/actions-runner/_work/server/server/lib/private/Files/Node/LazyFolder.php:65
/home/runner/actions-runner/_work/server/server/lib/private/Files/Node/LazyRoot.php:46
/home/runner/actions-runner/_work/server/server/lib/private/Files/View.php:1831
/home/runner/actions-runner/_work/server/server/tests/lib/Files/ViewTest.php:302