Computer.getUrl was incorrect when the slave had a space in its name.

This broke the context menu for actions contributed via TransientComputerActionFactory (at least).

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

@@ -622,7 +622,7 @@ public /*transient*/ abstract class Computer extends Actionable implements Acces
     }
 
     public String getUrl() {
-        return "computer/"+getDisplayName()+"/";
+        return "computer/" + Util.rawEncode(getDisplayName()) + "/";
     }
 
     /**