missing import statement.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@7918 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/node_monitors/NodeMonitor.java

@@ -5,6 +5,7 @@ import hudson.Functions;
 import hudson.model.Computer;
 import hudson.model.ComputerSet;
 import hudson.model.Describable;
+import hudson.model.Node;
 import hudson.util.DescriptorList;
 
 import java.util.logging.Level;