Close socket during initialization (#808)

If the global statsd instance is used before initialize() is
called (for example, statsd used to send metrics from a top-level of a
loaded module), statsd instance will already have a socket open when
we set connection parameters. To make sure they take effect, call
close_socket().

datadog/__init__.py

@@ -122,6 +122,7 @@ def initialize(
             statsd.host = statsd.resolve_host(statsd_host, statsd_use_default_route)
         if statsd_port:
             statsd.port = int(statsd_port)
+    statsd.close_socket()
     if statsd_namespace:
         statsd.namespace = text(statsd_namespace)
     if statsd_constant_tags:

tests/unit/dogstatsd/test_statsd.py

@@ -285,6 +285,12 @@ def test_dogstatsd_initialization_with_env_vars(self):
         self.assertEqual(dogstatsd.host, "myenvvarhost")
         self.assertEqual(dogstatsd.port, 4321)
 
+    def test_initialization_closes_socket(self):
+        statsd.socket = FakeSocket()
+        self.assertIsNotNone(statsd.socket)
+        initialize()
+        self.assertIsNone(statsd.socket)
+
     def test_default_route(self):
         """
         Dogstatsd host can be dynamically set to the default route.