Netty's PlatformDependent class attempts to open two files

which fails when running with a SecurityManager. We need to add a test for it as well as the following to the default policy:

grant codeBase "file://netty-common.jar" {
permission java.io.FilePermission "/etc/os-release", "read";
permission java.io.FilePermission "/usr/lib/os-release", "read";
}