Allow searching for IPs' logs

Update limitPerformer to search for IPs based on log_user_text, rather
than preventing any results from being returned. Also, make a
corresponding adjustment to list=logevents in the API, and remove
indexes to match the LogPager code.

Bug: 58691
Bug: 54404
Change-Id: Iae3f4ee5c7fba5b0b0f4f8fb3e67ac054c7b8dd7
Merge "Allow searching for IPs' logs"