Add Javadoc block on (interface) VirtualMachineManager

Author: GabrielBrascher

engine/api/src/main/java/com/cloud/vm/VirtualMachineManager.java

@@ -261,5 +261,8 @@ static String getHypervisorHostname(String name) {
 
     UserVm restoreVirtualMachine(long vmId, Long newTemplateId) throws ResourceUnavailableException, InsufficientCapacityException;
 
+    /**
+     * Returns true if the VM's Root volume is allocated at a local storage pool
+     */
     boolean isRootVolumeOnLocalStorage(long vmId);
 }