tests: make test_statsd more robust when executed along other asyncio-based tests

use a newly created event loop to consume events in test_timed_coroutine.
ome reason, executing this later test in the same test session as
swh/core/api/tests/test_async.py fail because the main event loop seems
to be closed by the test.

swh/core/tests/test_statsd.py

-# Copyright (C) 2018  The Software Heritage developers
+# Copyright (C) 2018-2019  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
@@ -312,7 +312,7 @@ class TestStatsd(unittest.TestCase):
             time.sleep(0.5)
             print("foo")
 
-        loop = asyncio.get_event_loop()
+        loop = asyncio.new_event_loop()
         loop.run_until_complete(print_foo())
         loop.close()