Clean up error messages in the previous CL.

TIL PLOG already logs the errno message, so it got logged twice
SignalCatcher::Output. Switch to PLOG for the corresponding messages in for brevity, and switch to LOG in the caller since the
errno message already has been logged by then.

Test: adb shell killall -QUIT system_server with a nearly full data
  partition; check logcat output.
Bug: 130025619

Change-Id: I973b04461de3492e3cb3e5855fc06e99efe32c0a
2 files changed