JMC agent: policy file is missing entry for test on Windows

In the JMC agent build on Windows the TestPermissionChecks agent test fails, since the surefire plugin puts the files it needs into the temp directory on Windows. On other platforms it uses target/surefire and this is included in the policy file used for the test. So for Windows to work, an entry for access to the temp directory (and all its subdirectories) is needed.