allow storage_controller error during pagebench (#8109)

## Problem

`test_pageserver_max_throughput_getpage_at_latest_lsn` is a pagebench
testcase which creates several tenants/timelines to verify pageserver
performance.


The test swaps environments around in the tenant duplication stage, so
the storage controller uses two separate db instances (one in the
duplication stage and another one in the benchmarking stage).
In the benchmarking stage, the storage controller starts without any
knowledge of nodes, but with knowledge of tenants (via
attachments.json). When we re-attach and attempt to update the scheduler
stats, the scheduler rightfully complains
about the node not being known. The setup should preserve the storage
controller across the two envs, but i think it's fine to just allow list
the error in this case.

## Summary of changes

add the error message 

`2024-06-19T09:38:27.866085Z ERROR Scheduler missing node 1``

to the list of allowed errors for storage_controller

test_runner/performance/pageserver/pagebench/test_pageserver_max_throughput_getpage_at_latest_lsn.py

@@ -209,3 +209,11 @@ def run_benchmark_max_throughput_latest_lsn(
             unit="ms",
             report=MetricReport.LOWER_IS_BETTER,
         )
+
+    env.storage_controller.allowed_errors.append(
+        # The test setup swaps NeonEnv instances, hence different
+        # pg instances are used for the storage controller db. This means
+        # the storage controller doesn't know about the nodes mentioned
+        # in attachments.json at start-up.
+        ".* Scheduler missing node 1",
+    )