app: exempt su from auditallow statement

Cut down on logspam during kernel_net_tests

Test: /data/nativetest64/kernel_net_tests/kernel_net_tests
Change-Id: Id19f50caebc09711f80b7d5f9d87be103898dd9a

public/app.te

@@ -201,6 +201,7 @@ userdebug_or_eng(`
     -platform_app
     -priv_app
     -shell
+    -su
     -system_app
     -untrusted_app_all
   } proc_net_type:{ dir file lnk_file } { getattr open read };