metrics: density: add kata support to memory usage script
metrics: density: add kata support to memory usage script

Add 'kata' detection and move to using the generic shim
and proxy vars.

Signed-off-by: Graham whaley <95f36e5ac6982f4574a5c449c37cf652e934d2b9@intel.com>

chavafg/tests,clearcontainers/tests,devimc/tests,chavafg/tests,devimc/tests,clearcontainers/tests