Fix bug where retries were not being properly set

Stung by the infamous isset() vs null issue in PHP.  Need to check if
the `retries` param is set OR if it is null, since the default set
of config options set `retries` to null.

This bug prevented retries from taking place, which meant that under
normal operating scenarios a bad host could take down the client with
an exception, when it normally should have retried on a different host.

src/Elasticsearch/Transport.php

@@ -80,7 +80,7 @@ public function __construct($hosts, $params, LoggerInterface $log)
         $this->seeds = $hosts;
         $this->setConnections($hosts);
 
-        if (isset($this->params['retries']) !== true) {
+        if (isset($this->params['retries']) !== true || $this->params['retries'] === null) {
             $this->params['retries'] = count($hosts);
         }
 

tests/Elasticsearch/Tests/ClientTest.php

@@ -47,10 +47,35 @@ public function testConstructorStringHost()
     public function testOneGoodOneBadHostNoException()
     {
         $params = array('hosts' => array (
+            '127.0.0.1:9201',
             '127.0.0.1:9200',
+        ));
+        $client = new Elasticsearch\Client($params);
+
+        // Perform three requests to make sure the bad host is tried at least once
+        $client->exists(array("index" => 'test', 'type' => 'test', 'id' => 'test'));
+        $client->exists(array("index" => 'test', 'type' => 'test', 'id' => 'test'));
+        $client->exists(array("index" => 'test', 'type' => 'test', 'id' => 'test'));
+
+    }
+
+
+    /**
+     * @expectedException Elasticsearch\Common\Exceptions\Curl\CouldNotConnectToHost
+     */
+    public function testOneGoodOneBadHostNoRetryException()
+    {
+        $params = array('hosts' => array (
             '127.0.0.1:9201',
+            '127.0.0.1:9200',
         ));
-        $this->client = new Elasticsearch\Client($params);
+        $params['retries'] = 0;
+        $client = new Elasticsearch\Client($params);
+
+        // Perform three requests to make sure the bad host is tried at least once
+        $client->exists(array("index" => 'test', 'type' => 'test', 'id' => 'test'));
+        $client->exists(array("index" => 'test', 'type' => 'test', 'id' => 'test'));
+        $client->exists(array("index" => 'test', 'type' => 'test', 'id' => 'test'));
 
     }