Revert of Revert "Fix masters_test presubmit_tests by using serialized sqlite access."

third_party/buildbot_8_4p1/buildbot/db/enginestrategy.py

Index: third_party/buildbot_8_4p1/buildbot/db/enginestrategy.py
diff --git a/third_party/buildbot_8_4p1/buildbot/db/enginestrategy.py b/third_party/buildbot_8_4p1/buildbot/db/enginestrategy.py
index 3d05cb6202327aa42c3fad40d390034c492704ef..cb711ce5d30dfe83b6e5c5c8eefb46edca43d772 100644
--- a/third_party/buildbot_8_4p1/buildbot/db/enginestrategy.py
+++ b/third_party/buildbot_8_4p1/buildbot/db/enginestrategy.py
@@ -80,6 +80,11 @@
         # in-memory databases need exactly one connection
         if not u.database:
             kwargs['pool_size'] = 1
+            max_conns = 1
+
+        # allow serializing access to the db
+        if 'serialize_access' in u.query:
+            u.query.pop('serialize_access')
             max_conns = 1
 
         return u, kwargs, max_conns