Fix api test script

Author: cdujeu

core/src/runTests.php

@@ -58,7 +58,7 @@ function apiPost($baseData, $url, $parameters, $private){
         echo "<style>*{font-family: Arial,sans-serif;}</style>";
         echo "<h3>Getting authentication token with user credentials</h3>";
         flush();
-        $tokens = file_get_contents("http://$user:$password@$host.$path/api/pydio/keystore_generate_auth_token/php_client");
+        $tokens = file_get_contents("http://${user}:${password}@${host}${path}/api/pydio/keystore_generate_auth_token/php_client");
         $data = json_decode($tokens, true);
         if(is_array($data)){
             echo "\n\nData is correctly decoded as JSON.";