Merge #20456: test: Fix intermittent issue in mempool_compatibility

fa05d19bd6 test: Fix intermittent issue in mempool_compatibility (MarcoFalke)

Pull request description:

  Fixes https://cirrus-ci.com/task/5141306890518528?command=ci#L6076

  The version is too old to understand getmempoolinfo()[loaded], so it is never called when starting (See https://cirrus-ci.com/task/5141306890518528?command=ci#L5541)

ACKs for top commit:
  achow101:
    ACK fa05d19bd6

Tree-SHA512: e912d5dff6236d2d4ac608f9f3b3e255cc2b611f36d79bfe4e2a940709833a947c682d7703327887e1753eab30b95eb2615d7e2c21ce4bca4f089e717cbb51c4

test/functional/mempool_compatibility.py

@@ -29,7 +29,7 @@ class MempoolCompatibilityTest(BitcoinTestFramework):
 
     def setup_network(self):
         self.add_nodes(self.num_nodes, versions=[
-            150200, # oldest version supported by the test framework
+            190100,  # oldest version with getmempoolinfo.loaded (used to avoid intermittent issues)
             None,
         ])
         self.start_nodes()
@@ -72,5 +72,6 @@ class MempoolCompatibilityTest(BitcoinTestFramework):
         assert old_tx_hash in old_node.getrawmempool()
         assert unbroadcasted_tx_hash in old_node.getrawmempool()
 
+
 if __name__ == "__main__":
     MempoolCompatibilityTest().main()