posts/index: fix search count tracking.

* Eliminate "&ms=1" url param.
* Only track simple single-tag searches (not multi-tag searches,
  metatags, negated tags, etc).

app/views/posts/index.html.erb

@@ -39,8 +39,6 @@
   <%= render "posts/partials/index/posts", :post_set => @post_set %>
 <% end %>
 
-<%= post_search_count_js %>
-
 <div id="saved-searches-nav">
   <%= render "saved_searches/interface" %>
 </div>
@@ -51,6 +49,14 @@
   <%= render "posts/partials/common/secondary_links" %>
 <% end %>
 
+<% if post_search_counts_enabled? && @post_set.query.is_simple_tag? && @post_set.current_page == 1 %>
+  <% if @post_set.post_count == 0 %>
+    <%= missed_post_search_count_js %>
+  <% else %>
+    <%= post_search_count_js %>
+  <% end %>
+<% end %>
+
 <% content_for(:html_header) do %>
   <%= render "posts/partials/index/seo_meta_tags" %>
 <% end %>