Merge changes from topic 'enable_persist_kernel_log' into nyc-mr1-dev

* changes:
  logcatd: trampoline persist.logd.logpersistd to logd.logpersistd
  logcatd: add stop and clear actions
  logcatd: Do not su for setprop
  logcat: allow comma-separate list of buffers
  logcat: clear when specifying file output
  logcat: Adjust help to make it more meaningful