The agents if they do not successfully check in for 45 days put themselves into a suspend mode and their licenses become available in the console. After 180 days the agent should uninstall itself from the machine. The link below talks about manual removal but does not include a script to send to uninstall. If the machines are on network you can deploy the agent again with the new policy then uninstall if you wish still. If not you can use a trick of getting the uninstall string from the registry. Each version will have an unique uninstall string. The location will be one of two options and will need to be searched.
In these locations look for a product in the string named folders that is Ivanti Patch for Windows Servers Agent or the older version is the Shavlik Protect Agent.
You can then use the uninstall string to start and modify it by removing the /X and replacing it with /quiet /norestart
I hope this is helpful and provides the information you need.