Handle cancellation due client disconnect

Handle client disconnect during the request handling gracefully.
E.g. if no primary selected, asyncio.sleep gets cancelled, and aiohttp
handles it correctly, and it should not trigger internal server errors.

karapace/rapu.py

@@ -330,6 +330,9 @@ async def _handle_request(
                 data = ex.body
                 status = ex.status
                 headers = ex.headers
+            except asyncio.CancelledError:
+                # Re-raise if aiohttp cancelled the task (e.g. client disconnected) without internal server error
+                raise
             except:  # pylint: disable=bare-except
                 self.log.exception("Internal server error")
                 headers = {"Content-Type": "application/json"}