adjusted visual styling for editing state of xblocks, html, and video components…

adjusted visual styling for editing state of xblocks, html, and video components which had extra padding applied to it from the container page xblock styling
STUD-1410

cms/static/sass/views/_unit.scss

@@ -1403,3 +1403,9 @@ body.unit .component {
     margin-top: ($baseline*1.5);
   }
 }
+
+body.unit .component.editing {
+  .xmodule_DiscussionModule, .xmodule_HtmlModule, .xblock {
+    margin-top: 0;
+  }
+}