The constraint errornoted is because IP locations are referenced in another table, tblAssets. You could circumvent this by changing the locationID for your assets prior to running a delete script. The script below will change all your asset ip locations to the built-in "undefined" and delete all other IP locations.
Update tblAssets set locationID = -1
GO
Delete from tsysIPlocations where locationID <> -1
GO
As noted above by Lansweeper themselves, always caution when tinkering with your database. Backup before making changes and test in dev if possible.