Merge pull request #3483 from varyvol/JENKINS-51816

[JENKINS-51816] Avoid the form to be sent when Enter is pressed.

core/src/main/resources/jenkins/install/SetupWizard/setupWizardConfigureInstance.jelly

@@ -103,14 +103,21 @@ THE SOFTWARE.
             </table>
           </div>
          <script>
-            $('root-url').focus();
+            var rootUrlField = $('root-url');
+            
+            rootUrlField.focus();
+            rootUrlField.onkeydown = function(event) {
+                if (event.keyCode == 13){
+                    event.preventDefault();
+                }
+            };
+
             (function setInitialRootUrlFieldValue(){
               var iframeUrl = window.location.href;
               // will let the trailing slash in the rootUrl 
               var iframeRelativeUrl = 'setupWizard/setupWizardConfigureInstance';
               var rootUrl = iframeUrl.substr(0, iframeUrl.length - iframeRelativeUrl.length);
               // to keep only the root url
-              var rootUrlField = $('root-url');
               rootUrlField.value = rootUrl
               // to adjust the width of the input,
               rootUrlField.size = Math.min(50, rootUrl.length);