testERP5TestNode: fix fake config

configparser read options as strings, node_quantity is not supposed to
be an int.

erp5/tests/testERP5TestNode.py

@@ -72,7 +72,7 @@ class ERP5TestNode(TestCase):
     config["slapos_directory"] = self.slapos_directory
     config["working_directory"] = self.working_directory
     config["software_directory"] = self.software_directory
-    config["node_quantity"] = 3
+    config["node_quantity"] = '3'
     config["test_suite_directory"] = self.test_suite_directory
     config["environment"] = self.environment
     config["log_directory"] = self.log_directory
@@ -598,7 +598,7 @@ shared = true
     for option in (
         ('--firefox_bin', part('firefox/firefox-slapos')),
         ('--frontend_url', 'http://frontend/'),
-        ('--node_quantity', 3),
+        ('--node_quantity', '3'),
         ('--xvfb_bin', part('xserver/bin/Xvfb')),
       ):
       parser.add_argument(option[0])