Update clean-oat-host after latest oat location changes.

oat and odex files are now located in a oat directory. In the
process of changing to the new directory, I realized we were also not
removing oat files from /system/priv-app.

This new rule just removes all oat/art/odex files found under
OUT_DIR.

bug:19945676

Change-Id: I4d21f3c9428afeacaca9753c21eceb1925ee537c