Add a test which checks expected number of reboots for SNO

Some tests may cause unexpected reboots of nodes. On HA setups this is checked by "should report ready nodes the entire duration of the test run" test, which ensures Prometheus metric for node readiness didn't flip.

On SNO however we can't use the metrics, as the prometheus will go down along with the node and the node would become ready again before Prometheus/kube-state-metrics is up again. For SNO we have to check that the node has expected number of reboots - number of "rendered-master/rendered-worker" MC + 1