wiki pages: fix redirects to exact matches during search.

Change wiki page search to redirect to exact matches only when using the
quick search bar. Fixes searches sometimes unexpectedly redirecting when
doing a regular (non-quick) search that happens to return a single result.

Also remove the logic that tries to expand the search when no results
are found. This will eventually be replaced with a smarter "did you mean?"
search.

test/functional/wiki_pages_controller_test.rb

@@ -22,12 +22,14 @@ class WikiPagesControllerTest < ActionDispatch::IntegrationTest
 
       should "list all wiki_pages (with search)" do
         get wiki_pages_path, params: {:search => {:title => "abc"}}
-        assert_redirected_to(wiki_page_path(@wiki_page_abc))
+        assert_response :success
+        assert_select "tr td:first-child", text: "abc"
       end
 
       should "list wiki_pages without tags with order=post_count" do
         get wiki_pages_path, params: {:search => {:title => "abc", :order => "post_count"}}
-        assert_redirected_to(wiki_page_path(@wiki_page_abc))
+        assert_response :success
+        assert_select "tr td:first-child", text: "abc"
       end
     end