fixed spinner positioning on inline discussions

lms/static/sass/_discussion.scss

@@ -1644,6 +1644,7 @@ body.discussion {
 
 .discussion-module {
   @extend .discussion-body;
+  position: relative;
   margin: 20px 0;
   padding: 20px;
   background: #f6f6f6 !important;
@@ -1658,6 +1659,10 @@ body.discussion {
     }
   }
 
+  .loading-animation {
+    background-image: url(../images/spinner-on-grey.gif);
+  }
+
   .discussion-show {
     position: relative;
     top: 3px;