remove the leading '/' to make browser prefer the right file name

changelog.html

@@ -58,6 +58,8 @@ Upcoming changes</a>
   <li class='major bug'>
     Maven builds failing with NullPointerException at the end.
     (<a href="https://issues.jenkins-ci.org/browse/JENKINS-10715">issue 10715</a>)
+  <li class=bug>
+    CLI jar download was making the browser prefer a wrong file name.
   <li class=bug>
     Link "Started by user XXX" broken on build status page if user name modified.
     (<a href="https://issues.jenkins-ci.org/browse/JENKINS-10698">issue 10698</a>)

core/src/main/java/jenkins/model/Jenkins.java

@@ -2791,7 +2791,7 @@ public class Jenkins extends AbstractCIBase implements ModifiableItemGroup<TopLe
     }
 
     public Slave.JnlpJar doJnlpJars(StaplerRequest req) {
-        return new Slave.JnlpJar(req.getRestOfPath());
+        return new Slave.JnlpJar(req.getRestOfPath().substring(1));
     }
 
     /**