JENKINS-10831 maven submodule build fails doing mkdir on master.

Remove the shadow copy of buildOn from MavenBuild.java and move the setter to
AbstractBuild to allow MavenModuleSetBuild.java to continue to set the
build node.

core/src/main/java/hudson/model/AbstractBuild.java

@@ -185,6 +185,16 @@ public abstract class AbstractBuild<P extends AbstractProject<P,R>,R extends Abs
         return builtOn;
     }
 
+    /**
+     * Set the name of the slave that the build was performed on.
+     * @param builtOn
+     * @since 1.429
+     */
+    public void setBuiltOnStr( String builtOn )
+    {
+        this.builtOn = builtOn;
+    }
+
     /**
      * Gets the nearest ancestor {@link AbstractBuild} that belongs to
      * {@linkplain AbstractProject#getRootProject() the root project of getProject()} that

maven-plugin/src/main/java/hudson/maven/MavenBuild.java

@@ -95,13 +95,6 @@ public class MavenBuild extends AbstractMavenBuild<MavenModule,MavenBuild> {
      * @since 1.98.
      */
     private List<ExecutedMojo> executedMojos;
-
-    /**
-     * Name of the slave this project was built on.
-     * Null or "" if built by the master. (null happens when we read old record that didn't have this information.)
-     * @since 1.394
-     */
-    private String builtOn;    
     
     public MavenBuild(MavenModule job) throws IOException {
         super(job);
@@ -293,26 +286,6 @@ public class MavenBuild extends AbstractMavenBuild<MavenModule,MavenBuild> {
         return super.getParent();
     }
 
-    /**
-     * @see hudson.model.AbstractBuild#getBuiltOn()
-     * @since 1.394
-     */
-    public Node getBuiltOn() {
-        if(builtOn==null || builtOn.equals(""))
-            return Jenkins.getInstance();
-        else
-            return Jenkins.getInstance().getNode(builtOn);
-    }
-
-    /**
-     * @param builtOn
-     * @since 1.394
-     */
-    public void setBuiltOnStr( String builtOn )
-    {
-        this.builtOn = builtOn;
-    }    
-
     /**
      * Runs Maven and builds the project.
      */