Disable enforcing of YARN container virtual memory limits in tests

Description
The Jepsen YARN tests sporadically fail because TM containers are exceeding their virtual memory limits:

Closing TaskExecutor connection container_1541436244107_0001_01_000005 because: Container [pid=32403,containerID=container_1541436244107_0001_01_000005] is running beyond virtual memory limits. Current usage: 970.2 MB of 2 GB physical memory used; 4.2 GB of 4.2 GB virtual memory used. Killing container.

By default YARN enforces a virtual memory limit of 2.1 times the requested physical memory. However, in my experiments, the virtual memory of a JVM process running the ClusterEntryPoint (without submitting job) is already in the region of 3.3 GB. Hence, the virtual memory enforcement should be disabled.

Acceptance Criteria

• yarn.nodemanager.vmem-check-enabled is false in yarn-site.xml