Clean up desktop mode logging

We were logging "isDesktopModeActive" each time it was called, spamming
logs. Removed it.
Each time visible task info was updated, we logged that an active task
was added, even if the task was already marked as active. Updated
logging to only log when task is first time added to active. Same with
removing from active tasks. Only logging when it is actually removed
from active tasks.

Bug: 244348395
Test: manual, updating logging, verified that the logs are printed
Change-Id: I55075c222763c6cb08f2d0e6770aed831b78a369