Fix JSInput test fixture

Clean up fixtures automatically between tests
- Nesting test fixture markup within a DIV allows Jasmine to
  automatically restore the fixture to a clean state between each test
  run.

Fix id attribute collision typo
- This looks like a copy/pasta gone wrong; the two test INPUT elements
  were both declared with the same id, `input_1`.

Remove trailing whitespace

common/static/js/capa/fixtures/jsinput.html

+<div>
 <section
-  id="inputtype_1" 
+  id="inputtype_1"
   data="getGrade"
   data-stored="{&quot;answer&quot;:&quot;{\&quot;cylinder\&quot;:true,\&quot;cube\&quot;:true}&quot;,&quot;state&quot;:&quot;{\&quot;selectedObjects\&quot;:{\&quot;cylinder\&quot;:true,\&quot;cube\&quot;:true}}&quot;}"
   data-getstate="getState"
@@ -10,11 +11,11 @@
 
   <div class="script_placeholder"/>
     <iframe
-      name="iframe_1" 
-      sandbox="allow-scripts 
-        allow-popups 
-        allow-same-origin 
-        allow-forms 
+      name="iframe_1"
+      sandbox="allow-scripts
+        allow-popups
+        allow-same-origin
+        allow-forms
         allow-pointer-lock"
       height="500"
       width="500"
@@ -24,7 +25,7 @@
   </div>
 </section>
 <section
-  id="inputtype_2" 
+  id="inputtype_2"
   data="getGrade"
   data-stored="{&quot;answer&quot;:&quot;{\&quot;cylinder\&quot;:true,\&quot;cube\&quot;:true}&quot;,&quot;state&quot;:&quot;{\&quot;selectedObjects\&quot;:{\&quot;cylinder\&quot;:true,\&quot;cube\&quot;:true}}&quot;}"
   data-getstate="getState"
@@ -35,16 +36,18 @@
 
   <div class="script_placeholder"/>
     <iframe
-      name="iframe_2" 
-      sandbox="allow-scripts 
-        allow-popups 
-        allow-same-origin 
-        allow-forms 
+      name="iframe_2"
+      sandbox="allow-scripts
+        allow-popups
+        allow-same-origin
+        allow-forms
         allow-pointer-lock"
       height="500"
       width="500"
       src="https://studio.edx.org/c4x/edX/DemoX/asset/webGLDemo.html">
     </iframe>
-    <input type="hidden" name="input_2" id="input_1" waitfor value="{&quot;answer&quot;:&quot;{\&quot;cylinder\&quot;:true,\&quot;cube\&quot;:true}&quot;,&quot;state&quot;:&quot;{\&quot;selectedObjects\&quot;:{\&quot;cylinder\&quot;:true,\&quot;cube\&quot;:true}}&quot;}">
+    <input type="hidden" name="input_2" id="input_2" waitfor value="{&quot;answer&quot;:&quot;{\&quot;cylinder\&quot;:true,\&quot;cube\&quot;:true}&quot;,&quot;state&quot;:&quot;{\&quot;selectedObjects\&quot;:{\&quot;cylinder\&quot;:true,\&quot;cube\&quot;:true}}&quot;}">
   </div>
-</section>
+</section>
\ No newline at end of file
+</div>
+