Refine perfstatsd daemon for io usage part

Bug: 115702127
Test: make perfstatsd -j100 && adb root && adb disable-verity && adb \
      reboot && sleep 5 && adb wait-for-device && adb root && sleep 5 && adb \
      remount && adb shell setenforce 0 && adb root && adb push \
      out/target/product/$TARGET_PRODUCT/vendor/bin/perfstatsd /vendor/bin/ && \
      adb shell chmod +x /vendor/bin/perfstatsd && adb reboot && adb \
      wait-for-device && adb root
Test: adb shell /vendor/bin/perfstatsd -d
Change-Id: I7ee9868a0d0cfdc7f96b25a129249f145d1f6bf1
4 files changed