Endpoints protected with INTERACT_ACROSS_USERS_FULL, such as startActivityAsUser, should only be used by modules signed with the platform cert. The NetworkStack needs to have the system server start the application so this restriction can be applied. Bug: 123846255 Test: flashed, captive portal works from primary and secondary user Change-Id: Ib3e427b3fd03ced80c02985e795f79b096a2ec9a