ResourceCalculatorProcessTree should be merged with existing ResourceCalculatorPlugin infractructure.
1. remove ResourceCalculatorProcessTree getResourceCalculatorProcessTree and move it to ResourceCalculatorPlugin as abstract member method.
2. LinuxResourceCalculatorPlugin will return procfsBasedProcessTree
3. method isAvailable() should not be needed, it is checked at lot of places. Removing it will simplify code. Unsupported operation systems get null from getResourceCalculatorPlugin and no plugin means no ResourceCalculatorProcessTree as well.
4. org.apache.hadoop.yarn.server.nodemanager.containermanager.monitor.ContainerMemoryMonitorImpl must be modified to work with ResourceCalculatorPlugin