ci: metrics: restore 'no KSM' on proxy for now

[grahamwhaley]

In #828 we removed the --ksm initial ksm disabling line that was used by the metric CI, on the grounds that we moved to the 'one proxy per VM' model - but - we still have the single global proxy installed to control KSM, as we do not have the 'ksm reaper' set up and running yet (clearcontainers/proxy#177).

Until clearcontainers/proxy#177 lands, we need to re-install the KSM disabling code.

[grahamwhaley]

/cc @jcvenegas @sboeuf @jodh-intel

[grahamwhaley]

See #913