[TEST] Fix for unescaped regex in tests

PHP doesn't like unescaped forward slashes that some tests use.  This
commit removes the beginning/end slash and replaces them with a new
delimeter

tests/Elasticsearch/Tests/YamlRunnerTest.php

@@ -131,7 +131,13 @@ private function assertFalsey($value)
     }
 
     private function assertRegex($pattern, $actual) {
-        $pattern .= "mx";
+        $pattern = trim($pattern);
+
+        // PHP doesn't like unescaped forward slashes, switch to a new delimeter
+        // to make life easier
+        $pattern = substr($pattern, 1, strlen($pattern)-2);
+        $pattern = "%$pattern%mx";
+        ob_flush();
         $result = preg_match($pattern, $actual, $matches);
         $this->assertEquals(1, $result);