Make the loading spinner toggle more explicit

Occasionally the loading spinner would stay visible after the tab
finished loading. This change makes the toggle explicit so that it's
always shown on `beforeSend`, and always hidden on `complete`.

Plus a bonus semi-colon eradication! 💥

app/assets/javascripts/merge_request_tabs.js.coffee

@@ -69,7 +69,7 @@ class @MergeRequestTabs
   scrollToElement: (container) ->
     if window.location.hash
       top = $(container + " " + window.location.hash).offset().top
-      $('body').scrollTo(top);
+      $('body').scrollTo(top)
 
   # Activate a tab based on the current action
   activateTab: (action) ->
@@ -139,13 +139,16 @@ class @MergeRequestTabs
         @diffsLoaded = true
         @scrollToElement(".diffs")
 
-  toggleLoading: ->
-    $('.mr-loading-status .loading').toggle()
+  # Show or hide the loading spinner
+  #
+  # status - Boolean, true to show, false to hide
+  toggleLoading: (status) ->
+    $('.mr-loading-status .loading').toggle(status)
 
   _get: (options) ->
     defaults = {
-      beforeSend: @toggleLoading
-      complete: @toggleLoading
+      beforeSend: => @toggleLoading(true)
+      complete:   => @toggleLoading(false)
       dataType: 'json'
       type: 'GET'
     }