Fixed some things with the test add functions

views/test/add.twig

@@ -37,7 +37,7 @@
         <div class="twelve columns">
           <label>
             Benchmarks:
-            <select id="benchmark-selector" class="u-full-width" name="test_benchmarks" multiple>
+            <select id="benchmark-selector" class="u-full-width" name="test_benchmarks[]" multiple>
               {% for b in benchmarks %}
                 <option value="{{ b.id }}">{{ b.name }}</option>
                 {% endfor %}