pytest: Clean up & remove 'leaks_process' marker

Fix these tests so they provision a singleton Manager and clean up after
themselves. Now they all pass so we can remove the marker.

BUG=chromium:1072136, chromium:1072139
TEST=`run_pytest -n 0`

Change-Id: Ic62b7c76219cbf26aabe5333d36bdcfb675bf1c4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2154753
Tested-by: Chris McDonald <cjmcdonald@chromium.org>
Commit-Queue: Chris McDonald <cjmcdonald@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/upload_symbols_unittest.py b/scripts/upload_symbols_unittest.py
index c9540c7..17080fa 100644
--- a/scripts/upload_symbols_unittest.py
+++ b/scripts/upload_symbols_unittest.py
@@ -19,6 +19,7 @@
 from six.moves import BaseHTTPServer
 from six.moves import socketserver
 from six.moves import urllib
+import pytest  # pylint: disable=import-error
 
 # We specifically set up a local server to connect to, so make sure we
 # delete any proxy settings that might screw that up.  We also need to
@@ -144,7 +145,7 @@
   """Simple HTTP server that forks each request"""
 
 
-@cros_test_lib.pytestmark_leaks_process
+@pytest.mark.usefixtures('singleton_manager')
 class UploadSymbolsServerTest(cros_test_lib.MockTempDirTestCase):
   """Tests for UploadSymbols() and a local HTTP server"""
 
@@ -565,7 +566,7 @@
     self.assertEqual(skipped, 10 * 2)
 
 
-@cros_test_lib.pytestmark_leaks_process
+@pytest.mark.usefixtures('singleton_manager')
 class UploadSymbolsTest(SymbolsTestBase):
   """Test UploadSymbols, along with most helper methods."""
   def setUp(self):