UX: Use the same default period for search logs index and term.

If the period is different, clicking through to view a term is confusing
because a different period will show a different set of stats.

app/assets/javascripts/admin/controllers/admin-search-logs-index.js.es6

@@ -1,6 +1,8 @@
+export const DEFAULT_PERIOD = "yearly";
+
 export default Ember.Controller.extend({
   loading: false,
-  period: "yearly",
+  period: DEFAULT_PERIOD,
   searchType: "all",
 
   searchTypeOptions: [

app/assets/javascripts/admin/controllers/admin-search-logs-term.js.es6

@@ -1,7 +1,9 @@
+import { DEFAULT_PERIOD } from "admin/controllers/admin-search-logs-index";
+
 export default Ember.Controller.extend({
   loading: false,
   term: null,
-  period: "quarterly",
+  period: DEFAULT_PERIOD,
   searchType: "all",
 
   searchTypeOptions: [