This change adds init.rc steps to:
* allow kernel tracing to be enabled via adb
* allow a limited set of kernel trace events to be enabled via adb
* allow the kernel trace to be read via adb
* allow all users to write to the kernel trace from userland
Bug: 6513400
Change-Id: Ic3c189b5697aa5edf88d2f507c932971bed6caff