Retry DROP DATABASE for tests

This partially reverts commit 3285fcb.

edb/testbase/server.py

@@ -764,7 +764,18 @@ def _extract_background_errors(metrics: str) -> str | None:
 
 
 async def drop_db(conn, dbname):
-    await conn.execute(f'DROP DATABASE {dbname}')
+    # net_worker (#7742) may issue a query while DROP DATABASE happens.
+    # This is a WIP bug that should be solved when adopting notification-
+    # driven net_worker, but hack around it with a retry loop for now.
+    # Without this, tests would flake a lot.
+    async for tr in TestCase.try_until_succeeds(
+        ignore=(edgedb.ExecutionError, edgedb.ClientConnectionError),
+        timeout=30
+    ):
+        async with tr:
+            await conn.execute(
+                f'DROP DATABASE {dbname};'
+            )
 
 
 class ClusterTestCase(BaseHTTPTestCase):