extract atop metrics more safely

Change-Id: I769aa0a9cda700001908dc5fac5fb2d87f19d533
leverage decorator package

Change-Id: I95336a336c9ac923de30643f1d33c814d1a1dfb8
make atop collector less verbose

Change-Id: I12863adf82b4be4f1cec0e12c432e9b6aba8a291