This test creates three pods with QoS of besteffort, burstable, and
guaranteed, respectively, which each contain a container that tries to
consume almost all the available memory at a rate of about 12Mi/10sec.

The expectation is that eviction will be initiated when the hard
memory.available<250Mi threshold is triggered, and that eviction will proceed
in the order of besteffort, then burstable. Since guaranteed pods should
only be evicted if something charged to the host uses more resources
than were reserved for it, we currently end the test when besteffort and
burstable have both been evicted.

Note that this commit also sets --eviction-hard=memory.available<250Mi
to enable eviction during tests.