Improve the appfunctions shell commands

1. execute-app-functions does not print the error message properly
It is because the readFromParcel flow does not invoke the supre
constructor. Also, now printing error code in toString too.

2. guard new commands with flags

Flag: EXEMPT changes in shell commands only
Test: run the command and observe the error

Change-Id: Idb6aa58e85584197e0ae1941d4c91bdd67bc7f08