Update InstallCommand test

They are god damn too long to execute because it launch external command (mostly related to doctrine).

So I've added a PHPUnit @group (`command-doctrine`) so that we can avoid launching them on a regular basis, like that:

`phpunit --exclude-group command-doctrine`

src/Wallabag/CoreBundle/Tests/Mock/InstallCommandMock.php

@@ -0,0 +1,22 @@
+<?php
+
+namespace Wallabag\CoreBundle\Tests\Mock;
+
+use Wallabag\CoreBundle\Command\InstallCommand;
+
+/**
+ * This mock aims to speed the test of InstallCommand by avoid calling external command
+ * like all doctrine commands.
+ *
+ * This speed the test but as a downside, it doesn't allow to fully test the InstallCommand
+ *
+ * Launching tests to avoid doctrine command:
+ *     phpunit --exclude-group command-doctrine
+ */
+class InstallCommandMock extends InstallCommand
+{
+    protected function runCommand($command, $parameters = array())
+    {
+        return $this;
+    }
+}